Primary invasive micropapillary carcinoma of the colon

Emerging and under-recognised patterns of colorectal carcinoma morphologies: a comprehensive review

While the overwhelming majority of colorectal carcinomas (CRC) are diagnosed as adenocarcinoma not otherwise specified, there are numerous under-recognised morphologic patterns of CRC. These patterns are recognised by the WHO, appear in reporting manuals for the American Joint Committee of Cancer, and/or are listed on synoptic reports, while many other variants have either fallen out of favour or are emerging as future bona fide patterns. Herein, we discuss 13 variants: serrated adenocarcinoma, micropapillary adenocarcinoma, medullary carcinoma, neuroendocrine carcinoma, mucinous adenocarcinoma, signet-ring cell carcinoma, adenosquamous carcinoma, adenoma-like adenocarcinoma, lymphoglandular complex-like CRC, carcinoma with sarcomatoid components, cribriform-comedo-type adenocarcinoma, undifferentiated carcinoma and low-grade tubuloglandular adenocarcinoma. The purpose of this review is to scrutinise these variants by assessing their clinical characteristics, morphologic cues, as well as pitfalls, and address their prognostic significance. Our analysis aims to bring clarity and updated understanding to these variants, offering valuable insights for pathologists. This contributes to more nuanced CRC diagnosis and treatment strategies, highlighting the importance of recognising a broad spectrum of morphologic patterns in CRC.

Clinical, pathological, genetics and intratumoural immune milieu of micropapillary carcinoma of the colon

AIM

Micropapillary carcinoma (MPC) is a recognised WHO variant of colonic carcinoma (CC), although little is known about its prognosis, immune microenvironment and molecular alterations. We investigated its clinical, pathological and immunological characteristics.

METHODS

We assessed 903 consecutive CCs and used the WHO definition to identify MPC. We recorded serrated and mucinous differentiation and mismatch repair (MMR) status. We performed immunohistochemistry and quantification on tissue microarrays for HLA class I/II proteins, beta-2-microglobulin (B2MG), CD8, CD163, LAG3, PD-L1, FoxP3, PD-L1and BRAF V600E.

RESULTS

We classified 8.6% (N=78) of CC as MPC. Relative to non-MPC, MPC was more often high grade (p=0.03) and showed serrated morphology (p<0.01); however, we found no association with extramural venous invasion (p=0.41) and American Joint Committee on Cancer stage (p=0.95). MPCs showed lower numbers of CD8 positive lymphocytes (p<0.01), lower tumour cell B2MG expression (p=0.04) and lower tumour cell PD-L1 expression (p<0.01). There was no difference in HLA class I/II, LAG3, FOXP3, CD163 and PD-L1 positive histiocytes. There was no association with MMR status or BRAF V600E relative to non-MPC. MPC was not associated with decreased disease-specific survival (p=0.36).

CONCLUSION

MPCs are associated with high-grade differentiation and a less active immune microenvironment than non-MPC. MPC is not associated with inferior disease-specific survival.

The Prognostic Value of Micropapillary Pattern in Colon Cancer and Its Role as a High-Risk Feature in Patients With Stage II Disease

BACKGROUND

The association of a micropapillary pattern with oncologic outcomes has not been fully studied in patients with colon cancer.

OBJECTIVE

We evaluated the prognostic value of a micropapillary pattern, especially for patients with stage II colon cancer.

DESIGN

A retrospective comparative cohort study using propensity score matching.

SETTING

This study was conducted at a single tertiary center.

PATIENTS

Patients with primary colon cancer undergoing curative resection from October 2013 to December 2017 were enrolled. Patients were grouped into micropapillary pattern positive or micropapillary pattern negative.

MAIN OUTCOME MEASUREMENTS

Disease-free survival and overall survival.

RESULTS

Of the eligible 2192 patients, 334 (15.2%) were with micropapillary pattern (+). After 1:2 propensity score matching, 668 patients with micropapillary pattern-negative status were selected. The micropapillary pattern-positive group showed significantly worse 3-year disease-free survival (77.6% vs 85.1%, p = 0.007). Three-year overall survival of micropapillary pattern-positive and micropapillary pattern-negative patients did not show a statistically significant difference (88.9% vs 90.4%, p = 0.480). In multivariable analysis, micropapillary pattern-positive was an independent risk factor for poor disease-free survival (HR 1.547, p = 0.008). In the subgroup analysis for 828 patients with stage II disease, 3-year disease-free survival deteriorated significantly in micropapillary pattern-positive patients (82.6% vs 93.0, p < 0.001). Three-year overall survival was 90.1% and 93.9% in patients positive and negative for micropapillary pattern, respectively ( p = 0.082). In the multivariable analysis for patients with stage II disease, micropapillary pattern-positive status was an independent risk factor for poor disease-free survival (HR 2.003, p = 0.031).

LIMITATIONS

Selection bias due to the retrospective nature of the study.

CONCLUSIONS

Micropapillary pattern-positive status may serve as an independent prognostic factor for colon cancer, especially for patients with stage II disease.

VALOR PRONSTICO DEL PATRN MICROPAPILAR Y SU PAPEL COMO CARACTERSTICA DE ALTO RIESGO EN PACIENTES CON CNCER DE COLON EN ESTADO II

ANTECEDENTES:La asociación del patrón micropapilar con los resultados oncológicos no ha sido completamente estudiada en pacientes con cáncer de colon.OBJETIVO:Evaluamos el valor pronóstico del patrón micropapilar, especialmente en pacientes con cáncer de colon en estadio II.DISEÑO:Estudio de cohortes comparativo y retrospectivo que utilize el emparejamiento por puntuación de propensiones.AJUSTE:Estudio realizado en un solo centro terciario.PACIENTES:Se incluyeron los pacientes con cáncer de colon primario sometidos a resección curativa desde octubre de 2013 hasta diciembre de 2017. Los pacientes se agruparon en patrón micropapilar positivo ( + ) o patrón micropapilar negativo ( - ).PRINCIPALES MEDIDAS DE RESULTADO:Sobrevida libre de enfermedad y la sobrevida global.RESULTADOS:De los 2192 pacientes elegibles, 334 (15,2%) tenían patrón micropapilar (+). Después de emparejar el puntaje de propensión 1:2, se seleccionaron 668 pacientes con patrón micropapilar (-). El grupo con patrón micropapilar (+) mostró una sobrevida libre de enfermedad significativamente inferior a los tres años (77,6% frente a 85,1%, p = 0,007). La sobrevida global a los tres años del patrón micropapilar (+) y del patrón micropapilar (-) no mostró una diferencia estadísticamente significativa (88,9 % frente a 90,4%, p = 0,480). En el análisis multivariable, el patrón micropapilar (+) fue un factor de riesgo independiente para una deficiente sobrevida libre de enfermedad (índice de riesgo 1,547, p = 0,008). En el análisis de subgrupos de 828 pacientes con enfermedad en estadio II, la sobrevida libre de enfermedad a los tres años se deterioró significativamente en los pacientes con patrón micropapilar (+) (82,6% frente a 93,0, p < 0,001). La sobrevida global a los tres años fué del 90,1% y del 93,9% en el patrón micropapilar (+) y el patrón micropapilar (-), respectivamente ( p = 0,082). En el análisis multivariable de los pacientes con enfermedad en estadio II, el patrón micropapilar (+) fue un factor de riesgo independiente para una sobrevida libre de enfermedad deficiente (índice de riesgo 2,003, p = 0,031).LIMITACIONES:Sesgo de selección debido a la naturaleza retrospectiva del estudio.CONCLUSIONES:El patrón micropapilar (+) sirve como factor pronóstico independiente para el cáncer de colon, especialmente para pacientes con enfermedad en estadio II. (Traducción-Dr. Xavier Delgadillo ).

Metabolome Sequencing Reveals that Protein Arginine-N-Methyltransferase 1 Promotes the Progression of Invasive Micropapillary Carcinoma of the Breast and Predicts a Poor Prognosis

Invasive micropapillary carcinoma (IMPC) of the breast is a special histopathologic type of cancer with a high recurrence rate and the biological features of invasion and metastasis. Previous spatial transcriptome studies indicated extensive metabolic reprogramming in IMPC, which contributes to tumor cell heterogeneity. However, the impact of metabolome alterations on IMPC biological behavior is unclear. Herein, endogenous metabolite-targeted metabolomic analysis was done on frozen tumor tissue samples from 25 patients with breast IMPC and 34 patients with invasive ductal carcinoma not otherwise specified (IDC-NOS) by liquid chromatography-mass spectrometry. An IMPC-like state, which is an intermediate transitional morphologic phenotype between IMPC and IDC-NOS, was observed. The metabolic type of IMPC and IDC-NOS was related to breast cancer molecular type. Arginine methylation modification and 4-hydroxy-phenylpyruvate metabolic changes play a major role in the metabolic reprogramming of IMPC. High protein arginine-N-methyltransferase (PRMT) 1 expression was an independent factor related to the poor prognosis of patients with IMPC in terms of disease-free survival. PRMT1 promoted H4R3me2a, which induced tumor cell proliferation via cell cycle regulation and facilitated tumor cell metastasis via the tumor necrosis factor signaling pathway. This study identified the metabolic type-related features and intermediate transition morphology of IMPC. The identification of potential targets of PRMT1 has the potential to provide a basis for the precise diagnosis and treatment of breast IMPC.

Molecular Pathology of Micropapillary Carcinomas: Is Characteristic Morphology Related to Molecular Mechanisms?

Micropapillary carcinoma is an entity defined histologically in many organs. It is associated with lymph node metastasis and poor prognosis. The main mechanism for its histopathologic appearance is reverse polarization. Although the studies on this subject are limited, carcinomas with micropapillary morphology observed in different organs are examined by immunohistochemical and molecular methods. Differences are shown in these tumors compared with conventional carcinomas regarding the rate of somatic mutations, mRNA and miRNA expressions, and protein expression levels. TP53 , PIK3CA , TERT , KRAS , EGFR , MYC , FGFR1 , BRAF , AKT1 , HER2/ERBB2 , CCND1 , and APC mutations, which genes frequently detected in solid tumors, have also been detected in invasive micropapillary carcinoma (IMPC) in various organs. 6q chromosome loss, DNAH9 , FOXO3 , SEC. 63 , and FMN2 gene mutations associated with cell polarity or cell structure and skeleton have also been detected in IMPCs. Among the proteins that affect cell polarity, RAC1, placoglobin, as well as CLDNs, LIN7A, ZEB1, CLDN1, DLG1, CDH1 (E-cadherin), OCLN, AFDN/AF6, ZEB1, SNAI2, ITGA1 (integrin alpha 1), ITGB1 (integrin beta 1), RHOA, Jagged-1 (JAG1) mRNAs differentially express between IMPC and conventional carcinomas. Prediction of prognosis and targeted therapy may benefit from the understanding of molecular mechanisms of micropapillary morphology. This review describes the molecular pathologic mechanisms underlying the micropapillary changes of cancers in various organs in a cell polarity-related dimension.

Expression of autocrine motility factor receptor (AMFR) in human breast and lung invasive micropapillary carcinomas

The aim of this study was to evaluate the clinicopathological significance of autocrine motility factor receptor (AMFR) expression in a variety of human invasive micropapillary carcinomas (IMPC). AMFR expression was compared in 111 samples of a variety of human IMPCs which had intrinsic non-micropapillary components and with 26 cases of control pulmonary adenocarcinoma (CPA, carcinoma without an IMPC component) by immunohistochemistry (IHC). In the 137 cases analysed, AMFR expression was significantly elevated in the IMPC components compared to the non-IMPC components (p = .005) and normal tissues (p < .001). AMFR expression was also higher in the IMPC samples compared to their intrinsic non-IMPC components (p = .0234). Between the 69 cases of lung IMPC and 26 cases of CPA, AMFR expression was notably higher in the IMPC components than in the CPA components (p = .0455). However, there was no significant difference between the non-IMPC components in the lung and the CPA components (p = .4584). Moreover, in breast cancer, elevated AMFR expression was not significantly correlated with mixed type or pure type IMPC (p = .5969) or with age, gender, T stage, or lymph node metastasis (LNM). Between IMPC and CPA of the lung, there was no statistical significance in age, T stage, and LNM, where AMFR expression was higher in IMPC (p = .0071). Thus this study demonstrated that AMFR was overexpressed in a variety of human IMPC components compared with non-micropapillary components. This suggests that AMFR expression is a potential new prognostic indicator for different types of human IMPC, which might thus be a new therapeutic target.

Increased Expression of LEF1 and β-Catenin in Invasive Micropapillary Carcinoma of the Breast is Associated With Lymphovascular Invasion and Lymph Node Metastasis

Invasive micropapillary breast carcinoma (IMPC) is a rare breast cancer subtype characterized by small tumor cell clusters with loss of stromal attachment, an inside-out growth appearance, and lymphotropism. IMPC is associated with high incidence of lymphovascular invasion (LVI) and lymph node metastasis. Activated Wnt signaling has been implicated in the metastasis of other aggressive breast tumors, including triple-negative and basal-like carcinomas. In this study, we tested whether activated Wnt signaling could be detected in IMPC. Upon ligand binding, the central mediator of the Wnt pathway, β-catenin, accumulates in the cytosol and translocates to the nucleus where it forms a complex with lymphoid enhancer-binding factor 1 (LEF1) to regulate transcription. We performed immunostaining for β-catenin and LEF1 on a well-annotated cohort of 40 breast tumors and nodal metastases displaying micropapillary histopathology. Strong nuclear accumulation of β-catenin was not observed, however a dim cytosolic and/or nuclear accumulation of β-catenin was sometimes seen in IMPC and this expression pattern was significantly associated with nodal metastasis. β-catenin expression correlated with the upregulation of LEF1 in IMPC. LEF1 expression was detected in 26 of 40 (65%) cases and was specifically enriched at the invasive front of the tumor and in tumor clusters undergoing LVI. Detection of LEF1 expression in the primary tumor was associated with an increased rate of LVI, lymph node metastasis, and disease relapse. LEF1 and β-catenin expression levels were significantly higher in metastases compared with primary tumors. In summary, this study demonstrates an association between the upregulation of β-catenin/LEF1 and the metastasis of IMPC.

Genomic alterations and evolution of cell clusters in metastatic invasive micropapillary carcinoma of the breast

Invasive micropapillary carcinoma (IMPC) has very high rates of lymphovascular invasion and lymph node metastasis and has been reported in several organs. However, the genomic mechanisms underlying its metastasis are unclear. Here, we perform whole-genome sequencing of tumor cell clusters from primary IMPC and paired axillary lymph node metastases. Cell clusters in multiple lymph node foci arise from a single subclone of the primary tumor. We find evidence that the monoclonal metastatic ancestor in primary IMPC shares high frequency copy-number loss of PRDM16 and IGSF9 and the copy number gain of ALDH2. Immunohistochemistry analysis further shows that low expression of IGSF9 and PRDM16 and high expression of ALDH2 are associated with lymph node metastasis and poor survival of patients with IMPC. We expect these genomic and evolutionary profiles to contribute to the accurate diagnosis of IMPC.

Spatial transcriptomics reveals gene expression characteristics in invasive micropapillary carcinoma of the breast

Invasive micropapillary carcinoma (IMPC) is a special histological subtype of breast cancer, featured with extremely high rates of lymphovascular invasion and lymph node metastasis. Based on a previous series of studies, our team proposed the hypothesis of "clustered metastasis of IMPC tumor cells". However, the transcriptomics characteristics underlying its metastasis are unknown, especially in spatial transcriptomics (ST). In this paper, we perform ST sequencing on four freshly frozen IMPC samples. We draw the transcriptomic maps of IMPC for the first time and reveal its extensive heterogeneity, associated with metabolic reprogramming. We also find that IMPC subpopulations with abnormal metabolism are arranged in different spatial areas, and higher levels of lipid metabolism are observed in all IMPC hierarchical clusters. Moreover, we find that the stromal regions show varieties of gene expression programs, and this difference depends on their distance from IMPC regions. Furthermore, a total of seven IMPC hierarchical clusters of four samples share a common higher expression level of the SREBF1 gene. Immunohistochemistry results further show that high SREBF1 protein expression is associated with lymph node metastasis and poor survival in IMPC patients. Together, these findings provide a valuable resource for exploring the inter- and intra-tumoral heterogeneity of IMPC and identify a new marker, SREBF1, which may facilitate accurate diagnosis and treatment of this disease.

Aberrant activation of Rho/ROCK signaling in impaired polarity switching of colorectal micropapillary carcinoma

Micropapillary carcinoma (MPC) is a morphologically distinctive form of carcinoma, composed of small nests of cancer cells surrounded by lacunar spaces. Invasive MPC is associated with poor prognosis. The nests of tumor cells in MPC reportedly exhibit reverse polarity, although the molecular mechanisms underlying MPC patterns are poorly understood. Using the cancer tissue-originated spheroid (CTOS) method, we previously reported polarity switching in colorectal cancer (CRC). When cultured in suspension, the apical membrane promptly switches from the outside surface of the CTOSs to the surface of the lumen inside the CTOSs under extracellular matrix (ECM)-embedded conditions, and vice versa. Here, we investigated two CTOS lines from CRC patient tumors with MPC lesions. Xenograft tumors from the CTOSs exhibited the MPC phenotype. The MPC-CTOSs did not switch polarity in vitro. Time-course analysis of polarity switching using real-time imaging of the apical membrane revealed that local switching was continually propagated in non-MPC-CTOSs, while MPC-CTOSs were unable to complete the process. Integrin β4 translocated to the outer membrane when embedded in ECM in both MPC and non-MPC-CTOSs. Protein levels, as well as the active form of RhoA, were higher in MPC-CTOSs. The suppression of RhoA activity by GAP overexpression enabled MPC-CTOSs to complete polarity switching both in vitro and in vivo, while overexpression of active RhoA did not affect polarity switching in non-MPC-CTOSs. Pretreatment with a ROCK inhibitor enabled MPC-CTOSs to complete polarity switching both in vitro and in vivo, although delayed treatment after becoming embedded in ECM failed to do so. Thus, the inability to switch polarity might be a cause of MPC, in which the aberrant activation of RhoA plays a critical role. © 2021 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Rare histological subtype of invasive micropapillary carcinoma in the ampulla of Vater: A case report

BACKGROUND

Carcinoma of the ampulla of Vater is an uncommon ampullo-pancreatobiliary neoplasm, and the most common histological type is adenocarcinoma with a tubular growth pattern. Invasive micropapillary carcinoma (IMPC) is an aggressive variant of adenocarcinoma in several organs that is associated with lymph node metastasis and poor prognosis. IMPC was first described as a histological subtype of breast cancer; however, IMPC of the ampulla of Vater is extremely rare, with only three articles reported in the English literature.

CASE SUMMARY

We have reported a case of IMPC of the ampulla of Vater in an 80-year-old man. Microscopically, the surface area of the carcinoma was composed of tubulopapillary structures mimicking intra-ampullary papillary-tubular neoplasm, and the deep invasive front area exhibited a pattern of IMPC. The carcinoma showed lymphatic invasion and extensive lymph node metastasis. The immunohistochemical study revealed mixed intestinal and gastric/pan-creatobiliary phenotypes.

CONCLUSION

This rare subtype tumor in the ampulla of Vater showed a histologically mixed phenotype and exhibited aggressive behavior.

Poorly differentiated clusters in colorectal cancer: a current review and implications for future practice

Poorly differentiated clusters (PDC), defined as small groups of ≥5 tumour cells without glandular differentiation, have gained recent attention as a promising prognostic factor in colorectal cancer (CRC). Numerous studies have shown PDC to be significantly associated with other adverse histopathological features and worse clinical outcomes. PDC may hold particular promise in stage II colon cancer, where risk stratification plays a critical role in patient selection for adjuvant chemotherapy. In addition, emerging evidence suggests that PDC can predict lymph node metastasis in endoscopically resected pT1 CRC, potentially helping the selection of patients for oncological resection. In 'head-to-head' comparisons, PDC grade has consistently outperformed conventional histological grading systems both in terms of risk stratification and reproducibility. With a number of large-scale studies now available, this review evaluates the evidence regarding the prognostic significance of PDC, considers its relationship with other emerging invasive front prognostic markers (such as tumour budding and stroma type), assesses its 'practice readiness', addressing issues such as interobserver reproducibility, scoring methodologies and special histological subtypes (e.g. micropapillary and mucinous carcinoma), and draws attention to ongoing challenges and areas in need of further study. Finally, emerging data on the role of PDC in non-colorectal cancers are briefly considered.

Cytological, histological, and molecular characteristics of pure invasive micropapillary carcinoma of pancreas: A case report

INTRODUCTION

Pure invasive micropapillary carcinoma (IMPC) is a rare histologic subtype of pancreatic cancer which has a high propensity for lymph node metastasis and poor prognosis.

PATIENT CONCERNS

An 81-year-old woman was admitted to our institution with a 3-month history of back pain. Computed tomography of the abdomen and pelvis confirmed the presence of a low-density mass in the tail of the pancreas.

DIAGNOSIS

Endoscopic ultrasound-guided fine needle aspiration cytology (FNAC) from the pancreatic mass showed small tumor cell clusters with three-dimensional aggregates and morula-like structures. The tumor was diagnosed as adenocarcinoma with micropapillary features.

INTERVENTIONS

The patient underwent radical antegrade modular pancreatosplenectomy and regional lymph node dissection. Histological examination showed small clusters of tumor cells that were closely adhered to one another. The cells were located in empty stromal spaces mimicking lymphovascular channels. All tumor cells showed reverse polarity, resulting in an "inside-out" pattern. An extensive search was performed, and no typical ductal adenocarcinoma component was found. The tumor measured 1.5 × 1.3 cm and invaded into the peripancreatic fat tissue without adjacent organ invasion. One of the 12 regional lymph nodes showed metastasis. Ion Torrent next-generation sequencing identified missense mutations in KRAS, TP53, and SMAD4 using the Oncomine Comprehensive Panel version 1.

OUTCOMES

Twelve months following surgical resection the patient remained healthy with no evidence of recurrence at clinical follow-up.

LESSONS

This report highlights the diagnostic features and molecular characteristics of pure pancreatic IMPC and the challenges with diagnosis by FNAC. A centralized and collaborative accumulation of additional cases of pure IMPC could further elucidate its pathogenesis.

Colorectal cancer with invasive micropapillary components (IMPCs) shows high lymph node metastasis and a poor prognosis: A retrospective clinical study

OBJECTS

The present study aimed to identify the clinicopathological characteristics of colorectal cancer (CRC) with invasive micropapillary components (IMPCs) and the relationship between different amounts of micropapillary components and lymph node metastasis.

METHODS

A cohort of 363 patients with CRC who underwent surgical treatment in the Second Affiliated Hospital of Zhejiang University School of Medicine between January 2013 and December 2016 were retrospectively reviewed. We compared the clinicopathological characteristics, including survival outcomes and immunohistochemical profiles (EMA, MUC1, MLH1, MSH2, MSH6, and PMS2), between CRC with IMPCs and those with conventional adenocarcinoma (named non-IMPCs in this study). Logistic regression was used to identify the association between IMPCs and lymph node invasion. A multivariate analysis was performed using the Cox proportional hazard model to evaluate significant survival predictors.

RESULTS

Among 363 patients, 76 cases had IMPCs, including 22 cases with a lower proportion of IMPCs (≤5%, IMPCs-L) and 54 cases with a higher proportion (>5%, IMPCs-H). Compared to the non-IMPC group, the IMPC group (including both IMPC-L and IMPC-H) had a lower degree of tumor differentiation (P = .000), a higher N-classification (P = .000), more venous invasion (P = .019), more perineural invasion (P = .025) and a later tumor node metastasis (TNM) stage (P = .000). Only tumor differentiation (P = .031) and tumor size (P = .022) were different between IMPCs-L and IMPCs-H. EMA/MUC1 enhanced the characteristic inside-out staining pattern of IMPCs, whereas non-IMPCs showed luminal staining patterns. The percentage of mismatch repair deficiency (dMMR) in the non-IMPC group was much higher than that in the IMPC group (14.7% vs 4.7%). The overall survival time of patients with IMPCs was significantly less than that of patients with non-IMPCs (P = .002), then that of IMPCs-H was lower than that of IMPCs-L (P = .030). Logistic regression revealed that patients with IMPCs were associated with lymph metastasis, regardless of the proportion of IMPCs. Multivariate analysis demonstrated both IMPCs-L and IMPCs-H as negative prognostic factors.

CONCLUSIONS

IMPCs are significantly associated with lymph node metastasis and poor outcome, and even a minor component (≤5%) may render significant information and should therefore be part of the pathology report.

Morphology and Molecular Features of Rare Colorectal Carcinoma Histotypes

Several histopathological variants of colorectal carcinoma can be distinguished, some associated with specific molecular profiles. However, in routine practice, ninety/ninety-five percent of all large bowel tumors are diagnosed as conventional adenocarcinoma, even though they are a heterogeneous group including rare histotypes, which are often under-recognized. Indeed, colorectal cancer exhibits differences in incidence, location of tumor, pathogenesis, molecular pathways and outcome depending on histotype. The aim is therefore to review the morphological and molecular features of these rare variants of intestinal carcinomas which may hold the key to differences in prognosis and treatment.

Glucose Metabolic Reprogramming and Cell Proliferation Arrest in Colorectal Micropapillary Carcinoma

Background

Micropapillary carcinoma (MPC) has been reported as an aggressive variant of colorectal carcinoma (CRC) associated with frequent lymphovascular invasion and poor outcome. Altered glycogen metabolism by metabolic reprogramming plays a critical role for cancer cell growth and survival. We aimed to investigate glucose metabolic reprogramming in colorectal MPC.

Methods

Immmunostains for Ki-67 and glucose transporter 1 (GLUT1) were performed on 10 colorectal MPCs. Real-time PCR analysis of expressions of GLUT1 and glycogen metabolizing enzymes: glycogen synthase (GYS1) and glycogen phosphorylase (PYGL) was performed on cultured monolayer and three-dimensional (3D) spheroid HCT116 colon cancer cells.

Results

GLUT1 was strongly expressed in MPC as compared to adjacent conventional glandular component, and was also significantly increased expression in 3D spheroids. Upregulation of GYS1 and PYGL was markedly increased in 3D spheroids. The proliferation rate (Ki-67) of MPC was significantly lower compared to conventional glandular component. The 3D spheroids showed increased cell cycle arrest. Our results demonstrate altered glycogen metabolism in colorectal MPC.

Conclusion

The reprogramming of glycogen metabolism in MPC provides a source of energy contributing to tumor cell survival in a low proliferation state. Targeting glucose-regulated metabolism may warrant consideration as possible MPC therapies.

Micropapillary adenocarcinoma of lung: Morphological criteria and diagnostic reproducibility among pulmonary pathologists

CONTEXT

Invasive micropapillary adenocarcinoma (MPC) is an aggressive variant of lung adenocarcinoma, frequently manifesting with advanced stage lymph node metastasis and decreased survival.

OBJECTIVE

Identification of this morphology is important, as it is strongly correlated with poor prognosis regardless of the amount of MPC component. To date, no study has investigated the morphological criteria used to objectively diagnose it.

DESIGN

Herein, we selected 30 cases of potential MPC of lung, and distributed 2 digital images per case among 15 pulmonary pathology experts. Reviewers were requested to diagnostically interpret, assign the percentage of MPC component, and record the morphological features they identified. The noted features included: columnar cells, elongated slender cell nests, extensive stromal retraction, lumen formation with internal epithelial tufting, epithelial signet ring-like forms, intracytoplasmic vacuolization, multiple nests in the same alveolar space, back-to-back lacunar spaces, epithelial nest anastomosis, marked pleomorphism, peripherally oriented nuclei, randomly distributed nuclei, small/medium/large tumor nest size, fibrovascular cores, and spread through air-spaces (STAS).

RESULTS

Cluster analysis revealed three subgroups with the following diagnoses: "MPC", "combined papillary and MPC", and "others". The subgroups correlated with the reported median percentage of MPC. Intracytoplasmic vacuolization, epithelial nest anastomosis/confluence, multiple nests in the same alveolar space, and small/medium tumor nest size were the most common criteria identified in the cases diagnosed as MPC. Peripherally oriented nuclei and epithelial signet ring-like forms were frequently identified in both the "MPC" and "combined papillary and MPC" groups.

CONCLUSIONS

Our study provides objective diagnostic criteria to diagnose MPC of lung.

High-grade ovarian serous carcinomas: Significant correlation of histologic patterns with IMP3 and E-Cadherin predicting disease recurrence and survival

Most high-grade serous carcinomas (HGSC) of the ovary are advanced stage tumors with early recurrences. However, some tumors do not recur and have a better survival. We identified such cases of HGSC and compared those with the cases that recurred and assessed the relationship between patterns of invasion (intracystic, IC; micropapillary, MP; nonpapillary, NP) with IMP3 and E-Cadherin expression, and evaluated their predictive role in recurrence and survival. The study comprised of seventeen tumors recurred within 18 months of follow-up and 14 cases that did not recur with a minimum follow-up of 49 months. 73% tumors with predominantly MP pattern recurred, while only 27% of non-recurrent tumors showed this pattern. In contrast, predominant NP and IC patterns were seen in 71% of the non-recurrent and in 35% of recurrent tumors. 67.7% tumors expressed IMP3 and all cases expressed E-Cadherin. The tumors with a higher percentage of destructive invasion showed higher IMP3 positivity and greater chances of recurrence, whereas tumors with higher percentage of pushing invasion showed lower IMP3 positivity and lesser chances of recurrence (p = 0.02). IMP3-negative tumors had lower odds of recurrence than IMP3-positive ones (p = 0.01). The patients with negative IMP3 staining had a significantly higher OS than those with IMP3 positive tumors (p = 0.01), regardless of the histologic patterns. Also, reduction in E-Cadherin staining in the metastatic site led to poor DFS (p = 0.016) and OS (p = 0.006). IMP3 may serve as a useful prognostic marker that can stratify patients of advanced stage, high-grade serous carcinomas into two distinct subsets: majority with early recurrence with an infiltrative pattern of invasion and IMP3 positivity particularly in the MP areas; and a smaller subset that do not show early recurrence having pushing borders and are IMP3 negative. Also, E-Cadherin showed significant decrease in expression in the metastatic site of the recurrent cases.

Prognostic and therapeutic role of HER2 expression in micropapillary carcinoma of the bladder

Micropapillary carcinoma of the bladder (MPBC) is a variant type of infiltrating urothelial carcinoma, which portends a poor biological behavior in terms of disease stage at first diagnosis and clinical outcome; its peculiar morphology raises issues concerning the ability of tumor detection by imaging techniques and proper biopsy procedure, and the appropriate treatment for non-muscle infiltrating and muscle-infiltrating MPBC remains a matter of debate. On the basis of its established prognostic and therapeutic role in breast and gastro-esophageal cancer in the first instance, the human epidermal growth factor receptor-2 (HER2) has been investigated in selected case series of MPBC over the last 10 years. The aim of the present review was to summarize the existing evidence on HER2 status in MPBC, and to discuss its present and future utility in risk assessment and treatment choice of this uncommon, yet aggressive, disease.

Colon Metastasis From Microscopic Serous Carcinoma of the Fallopian Tube Fimbria Mimicking a Primary Colon Cancer

Metastatic diseases rarely develop in the colorectum, and diagnosing colorectal metastasis by biopsy without history of a malignant tumor or clinical information of a primary tumor is challenging. A 65-year-old woman with a 6-month history of constipation and diarrhea was admitted to our hospital and diagnosed with rectosigmoid colonic micropapillary carcinoma. Low anterior resection was performed after neoadjuvant chemotherapy. Because the lipoleiomyoma in the uterus obstructed the operator’s vision, total hysterectomy and bilateral salpingo-oophorectomy were performed. Examination of the colon and adnexa, together with immunohistochemical studies, revealed that the colonic tumor was actually serous carcinoma that had metastasized from the left fimbria of the fallopian tube. Retrospective immunohistochemical examination of the colon biopsy specimen suggested carcinoma with a Müllerian immunophenotype. When a colon biopsy reveals carcinoma with an invasive micropapillary pattern without a component of conventional tubular adenocarcinoma, immunohistochemical examination should be performed to rule out the possibility of metastasis.

Study of Histopatological Parameters of Gastric Carcinomas with Micropapillary Component

Micropapillary carcinoma was recently identified as a carcinoma variant characterized by the presence of small clusters of tumor cells located in optically empty spaces. The study included a number of 14 cases represented by surgical excision specimens diagnosed with gastric carcinoma (tubular, papillary and signet-ring) which associated the micropapillary component in variable proportions. Regarding the low-grade tubular carcinomas, the micropapillary component represented less than 25% of the tumor, while in the high-grade tubular carcinomas and papillary carcinomas it represented 25-50%. Among signet-ring carcinomas, the micropapillary component had a percentage of over 50. The depth of invasion was frequently associated with T3 and T4 categories. Lymph nodes metastasis were found in ten cases and distant metastasis were present in three cases. Recognition of the micropapillary component associated with gastric carcinoma represents an aspect of great importance because it is frequently correlated with unfavorable prognosis parameters.

Precise pathologic diagnosis and individualized treatment improve the outcomes of invasive micropapillary carcinoma of the breast: a 12-year prospective clinical study

Invasive micropapillary carcinoma of the breast is a histologic subtype of breast cancer and associated with high incidence of lymphovascular invasion, lymph node metastasis and poor prognosis. The aim of this prospective study was to investigate the impact of precise pathologic diagnosis and individualized treatment on the outcomes of invasive micropapillary carcinoma of the breast. The study group included 2299 women with invasive micropapillary carcinoma diagnosed at Tianjin Medical University Cancer Institute and Hospital between January 2004 and December 2015. In the study group, specimens were examined with the method of whole-specimen orientation and serial sectioning, and patients received precise pathological diagnosis and individualized treatment. The control group of invasive micropapillary carcinoma consisted of 163 cases, identified through a retrospectively review of 9056 invasive carcinomas diagnosed at our institution between January 1989 and December 2003 using the standard pathology-evaluation method (i.e., not using the whole-specimen orientation and serial-sectioning method). The clinicopathological features, treatments and outcomes were compared between the two groups. The incidence of invasive micropapillary carcinoma in the study group was 6% (2299/39,714 cases), significantly higher than that of the control group (2%; 163/9056 cases). The 5-year disease-free survival in the study group was significantly higher than that in the control group (83.8 vs.45.4%; p < 0.05). The 5-year overall survival was significantly increased from 57.4% in the control group to 90.9% in the study group (p < 0.05). In the multivariate analysis, lymphovascular invasion, estrogen receptor status and lymph node metastasis were independent prognostic factors. Although invasive micropapillary carcinoma of the breast is associated with poor prognosis, precise pathologic diagnosis and individualized treatment improved the disease-free survival and overall survival of invasive micropapillary carcinoma patients. Precise pathological diagnosis is the premises for individualized treatments and for improving the outcomes of patients with invasive micropapillary carcinoma of the breast.

The clinicopathological significance of micropapillary pattern in colorectal cancers

The aim of the present study is to elucidate the clinicopathological significance and prognostic role of micropapillary pattern (MPP) in colorectal cancer (CRC). We investigated the correlation between the presence of MPP and clinicopathological characteristics and prognosis in 266 CRCs. In addition, the clinicopathological significance of MPP in mucin pools was investigated and compared to pure MPP, which is not associated with mucin pools. MPP, regardless of its proportion in the overall tumor, was found in 74 of 266 CRCs (27.8%). The rate of MPP in proportions ≥5% was 9.4% (25 of 266 cases). CRC with MPP showed higher rates of vascular and lymphatic invasion, higher metastatic lymph node ratio, and higher pT stage compared to CRC without MPP. In addition, increasing proportion of MPP in overall tumor showed more frequent vascular and lymphatic invasions (P = .002 and P = .008, respectively). Among 74 CRCs with MPP, 25 CRCs were found in mucin pools (33.8%). These cases were more right-sided and poorly differentiated with less frequent lymphatic invasion and lymph node metastasis, compared to CRCs with pure MPP. The presence of MPP significantly correlated with worse overall survival (P = .010). In 74 CRCs with MPP, overall survival significantly differed between pure MPP and MPP in mucin pools (P = .003). Taken together, our data suggest that the presence of MPP significantly correlated with aggressive tumor behavior and worse survival in CRC. In addition, the clinicopathological significance of MPP in mucin pools differed from CRC with pure MPP.

Overexpression of β1 integrin contributes to polarity reversal and a poor prognosis of breast invasive micropapillary carcinoma

Invasive micropapillary carcinoma (IMPC) of the breast is a highly aggressive breast cancer. Polarity reversal exemplified by cluster growth is hypothesized to contribute to the invasiveness and metastasis of IMPC. In this study, we demonstrate that levels of β1 integrin and Rac1 expression were greater in breast IMPC than in invasive breast carcinoma of no specific type and paraneoplastic benign breast tissue. We show that silencing β1 integrin expression using the β1 integrin inhibitor AIIB2 partially restored polarity in IMPC primary cell clusters and downregulated Rac1. Thus, overexpression of β1 integrin upregulates Rac1. Univariate analysis showed that overexpression of β1 integrin and Rac1 was associated with breast cancer cell polarity reversal, lymph node metastasis, and poor disease-free survival in IMPC patients. Multivariate analysis revealed that polarity reversal was an independent predictor of poor disease-free survival. These findings indicate that overexpression of β1 integrin and the resultant upregulation of Rac1 contribute to polarity reversal and metastasis of breast IMPC, and that β1 integrin and Rac1 could be potential prognostic biomarkers and targets for treatment of breast IMPC.

Invasive Micropapillary Carcinoma of the Breast: An Update

CONTEXT

-Invasive micropapillary carcinoma (IMPC) is a distinct variant of mammary carcinoma in which tumor cells are arranged in morulelike clusters devoid of fibrovascular cores and situated within empty stromal spaces. Identification of IMPC can be achieved by the assessment of morphologic features in conjunction with the characteristic "inside-out" staining pattern of epithelial membrane antigen and sialyl Lewis X highlighted by immunohistochemical analysis. Although recognizing micropapillary architecture is often not challenging, the criteria for distinguishing between mixed and pure IMPC remain imprecise. Some mucin-producing carcinomas can also have micropapillary histology, but there is no consensus on whether these tumors are variants of IMPC or mucinous carcinomas. The molecular genetic studies demonstrate that IMPCs have distinct molecular genetic profiles, supporting the theory that they constitute distinct pathologic entities. However, genomic analyses have not identified any specific genomic aberration that may explain the distinctive morphology and clinical behavior of IMPC.

OBJECTIVE

-To provide an overview on the current concepts in the diagnosis and pathogenesis of IMPC of the breast, incorporating recent molecular genetic advances and prognosis-based reclassification.

DATA SOURCES

-PubMed search and the cited references were reviewed.

CONCLUSIONS

-The recent evolution of prognosis-based reclassification and molecular genetic advances has enhanced our knowledge of the pathogenesis of IMPC of the breast. Additional studies might reveal consistent molecular alterations that underlie the formation of the inside-out growth pattern, and they might elucidate the molecular mechanisms responsible for the unfavorable clinical behavior of IMPC.

Micropapillary colorectal carcinoma: clinical, pathological and molecular properties, including evidence of epithelial-mesenchymal transition

AIMS

Colorectal carcinoma (CRC) with micropapillary (MP) features has only been described recently and is still being characterized.

METHODS AND RESULTS

We reviewed the clinicopathological and molecular features of 42 CRC with MP features. Twenty-nine cases were also evaluated for immunohistochemical evidence of epithelial-mesenchymal transition (EMT). The extent of MP features within our cohort ranged from 5% (13 cases) to 100% (one case). Twenty-seven cases featured prominent cribriforming with dirty necrosis in the non-MP component; nine displayed mucinous features. Twenty-four of 29 cases (83%) demonstrated evidence of EMT. Thirty-six cases (86%) showed advanced T-category (pT3 or pT4), 31 (74%) had lymph node metastases and 23 (55%) had distant metastases. Median overall follow-up was 36 months. Seventeen patients (40%) died of disease, with median survival of 23 months. Mutations were seen in 17 of 31 tested cases (55%), including 11 KRAS mutations and four BRAF V600E mutations. Microsatellite instability testing was performed on 21 cases; all were microsatellite-stable. Compared to a cohort of 972 conventional CRC, MP CRC was more likely to present as stage IV disease (P < 0.001), but patients with MP CRC showed no significant differences in overall survival after adjusting for stage.

CONCLUSIONS

Micropapillary features in CRC portend a high likelihood of advanced local disease and distant metastases. MP CRC is often associated with a cribriform pattern elsewhere in the tumour and cystic nodal metastases with prominent necrosis. They also show frequent mutations in KRAS and BRAF. Immunohistochemical evidence of EMT is common in MP CRC.

Reversed polarity of the glandular epithelial cells in micropapillary carcinoma of the large intestine and the EMA/MUC1 immunostain

Micropapillary carcinoma of the colon and rectum is associated with an adverse prognosis. This tumour type displays reverse polarity of the tumour cells and is stated to be characterised by an inside-out epithelial membrane antigen (EMA)/MUC1 staining. Nine cases of primary colorectal carcinoma and one omental metastasis were studied by means of immunohistochemistry, using antibodies to detect EMA, MUC1, MUC2, MUC3, MUC5AC, MUC6, CD10, CA125, carcinoembryonic antigen (CEA). The inside-out pattern staining with EMA/MUC1 ranged from diffuse circumferential through focal and partial to negative, but in some cases CEA, MUC3 and CD10 also showed this pattern staining, sometimes more clearly than did EMA or MUC1. The reverse polarity of colorectal micropapillary carcinomas is sometimes better visualised by immunostains other than EMA/MUC1.

A Concurrence of Adenocarcinoma with Micropapillary Features and Composite Glandular-Endocrine Cell Carcinoma in the Stomach

We report a unique case of synchronous double primary gastric cancer consisting of adenocarcinoma components with micropapillary features and composite glandular-endocrine cell carcinoma components. The patient was a 53-year-old man presenting with a 6-month history of epigastric pain and diarrhea. A subtotal gastrectomy was performed. Histologically, one tumor was composed of micropapillary carcinoma components (50%) with tight clusters of micropapillary aggregates lying in the empty spaces, admixed with moderately differentiated adenocarcinoma components. MUC-1 was expressed at the stromal edge of the micropapillary component. The other tumor was composed of atypical carcinoid-like neuroendocrine carcinoma (50%), adenocarcinoid (30%), and adenocarcinoma components (20%). The neuroendocrine components were positive for CD56, synaptophysin, chromogranin, and creatine kinase. The adenocarcinoid components were positive for both carcinoembryonic antigen and neuroendocrine markers (amphicrine differentiation). This case is unique, due to the peculiar histologic micropapillary pattern and the histologic spectrum of adenocarcinoma adenocarcinoid-neuroendocrine carcinoma of the synchronous composite tumor.

Primary micropapillary carcinoma of the colon with submucosal invasion: A case report

We present a case of invasive micropapillary carcinoma (IMPC) of the colon treated by endoscopic resection following magnifying endoscopy. A 47-year-old woman visited our hospital for follow-up of a positive fecal occult blood test. Colonoscopy revealed a semi-pedunculated reddish polyp, the surface of which showed gentle irregularity, and mild tension in the sigmoid colon. Magnifying colonoscopy with narrow band imaging revealed an irregular surface pattern with heterogeneity in vascular diameter and distribution. Magnifying endoscopic findings using crystal violet staining showed an irregular pit pattern with an expansion of stromal areas. Endoscopic resection of the sigmoid colon tumor was performed, and the histology of the resected specimen primarily revealed a micropapillary component with a small moderately differentiated adenocarcinoma component that massively invaded into the submucosal layer, accompanied by lymphatic invasion, although the tumor was very small (7 mm in diameter, smaller than any in previous reports). Laparoscopy-assisted sigmoidectomy and regional lymph node resection were performed; neither cancer nor lymph node metastases were present. This is the first report of a case with early-stage colonic IMPC observed with magnifying colonoscopy.

Mammary Invasive Micropapillary Carcinoma in Cats: Clinicopathologic Features and Nuclear DNA Content

Invasive micropapillary carcinoma (IMC) is a variant of infiltrating ductal carcinoma of the breast associated with poor outcome. In this study, we report 16 carcinomas of the feline mammary gland displaying histologic features that correspond to IMC of the breast in women. The clinicopathologic findings, overall survival time, disease-free survival time, and nuclear DNA content of these cats were compared with 65 more common invasive mammary carcinomas (other feline mammary carcinoma [FMC]) of nonspecified type. IMC was associated with larger tumor size, higher histologic grade ( P < .0001), deeper muscle invasion ( P = .004), and more frequent lymphovascular invasion and nodal metastases ( P = .009 and P = .001, respectively) than other FMCs. The aneuploid pattern was more frequent in IMC lesions. IMCs were also associated with lower survival rates. In summary, all cases of feline IMC were associated with clinicopathologic features of high biologic aggressiveness and should be classified as independent histologic types of FMC.

Invasive micropapillary component and its clinico-histopathological significance in patients with colorectal cancer

Micropapillary components are located in distinct, empty spaces resembling lymphatic vessels and consist of clusters of cancer cells that adhere tightly to one another. These structures do not have a fibrovascular core. Invasive micropapillary components (IMPCs) exhibit reverse polarity, which results in a characteristic 'inside-out' structure. The aim of the present study was to examine the histological significance of the micropapillary component in colorectal carcinoma compared with conventional colorectal adenocarcinoma. Among 115 patients, 5 (4.3%) were diagnosed with a micropapillary colorectal component based on hematoxylin and eosin staining and immunohistochemical analysis. To exclude identification of poorly-differentiated clusters of adenocarcinoma cells in the lymphatic vessels, immunohistochemical analysis with D2-40 was performed, and epithelial membrane antigen was used to confirm the specific 'inside-out' structure of IMPCs. IMPCs were observed to positively correlate with histopathological type (P=0.001) and tumor invasion in venous vessels (P=0.033). Furthermore, the presence and number of lymph node metastases was greater in IMPC cases compared with conventional carcinoma cases; however, these differences were not statistically significant (P=0.087 and P=0.094, respectively). In addition, IMPC cases were not significantly associated with the presence of inflammatory infiltrate in the invasive front of the tumor (P=0.098). Therefore, the present study indicates that the IMPC serves a histopathological and prognostic role in the diagnosis of colorectal cancer due to its aggressive and invasive behavior. IMPC is rare in cases of colorectal cancer and remains a great diagnostic challenge in pathomorphology with further detailed investigation required in the future.

Consensus and conflict in invasive micropapillary carcinoma: a case report and review of the literature

Invasive micropapillary carcinoma (IMPC) is an aggressive histologic subtype of adenocarcinoma that has been gaining increased attention over the past twenty years. It is important to recognize IMPC due to its strong association with early lymphovascular invasion (LVI), high risk of lymph node metastasis, perineural invasion and poor prognosis. Controversies regarding IMPC include differentiating from retraction artifact and mimics, clinical significance of proportion of micropapillary component (MC), pathogenesis, biologic nature of the entity and consequently terminology, etc. We herein present a case of rectal IMPC arising from a tubulovillous adenoma. Since HER2 over-expression has been reported in IMPC of the breast and the bladder but never in the colorectum, given the availability of HER2 targeted therapy, HER2 protein expression in our case is examined by immunohistochemical study which shows weak incomplete membrane staining in less than 5% of cells. Literature is reviewed with emphasis on colorectal IMPC as well as aforementioned controversial topics. In summary, more study is needed to resolve the conflicts and build consensus on IMPC.

Phagocytosis (cannibalism) of apoptotic neutrophils by tumor cells in gastric micropapillary carcinomas

AIM: To identify those with a micropapillary pattern, ascertain relative frequency and document clinicopathological characteristics by reviewing gastric carcinomas.

METHODS: One hundred and fifty-one patients diagnosed with gastric cancer who underwent gastrectomy were retrospectively studied and the presence of a regional invasive micropapillary component was evaluated by light microscopy. All available hematoxylin-eosin (HE)-stained slides were histologically reviewed and 5 tumors were selected as putative micropapillary carcinoma when cancer cell clusters without a vascular core within empty lymphatic-like space comprised at least 5% of the tumor. Tumor tissues from these 5 invasive gastric carcinomas were immunostained using an anti-mucin 1 (MUC1) antibody (clone MA695) to detect the characteristic inside-out pattern and with D2-40 antibody to determine the presence of intratumoral lymph vessels. Detection of intraepithelial neutrophil apoptosis was evaluated in consecutive histological tissue sections by three independent methods, namely light microscopy with HE staining, the conventional terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling (TUNEL) method and immunohistochemistry for activated caspase-3 (clone C92-605).

RESULTS: Among 151 gastric cancers resected for cure, 5 (3.3%) were adenocarcinomas with a micropapillary component. Four of the patients died of disease from 6 to 23 mo and one patient was alive with metastases at 9 mo. All patients had advanced-stage cancer (≥ pT2) and lymph node metastasis. Positive MUC1 immunostaining on the stroma-facing surface (inside-out pattern) of the carcinomatous cluster cells, together with negative immunostaining for D2-40 in the cells limiting lymphatic-like spaces, confirmed the true micropapillary pattern in these gastric neoplasms. In all five cases, several micropapillae were infiltrated by neutrophils. HE staining, TUNEL assay and immunostaining for caspase-3 demonstrated apoptotic neutrophils within cytoplasmic vacuoles of tumor cells. These data suggest phagocytosis (cannibalism) of apoptotic neutrophils by micropapillary tumor cells. Tumor cell cannibalism is usually found in aggressive tumors with anaplastic morphology. Our data extend these observations to gastric micropapillary carcinoma: a tumor histotype analogously characterized by aggressive behavior and poor prognosis. The results are of interest because they raise the intriguing possibility that neutrophil cannibalism by tumor cells may be one of the mechanisms favoring tumor growth in gastric micropapillary carcinomas.

CONCLUSION: This is the first study showing phagocytosis (cannibalism) of apoptotic neutrophils by tumor cells in gastric micropapillary carcinomas.

The presence of extensive retraction clefts in invasive breast carcinomas correlates with lymphatic invasion and nodal metastasis and predicts poor outcome: a prospective validation study of 2742 consecutive cases

We previously reported that the presence of extensive retraction clefts (RC) in breast cancers correlates with increasing tumor size and grade as well as lymphatic tumor spread and predicts poor outcome. This study is a prospective validation of our prior results. Consecutive cases of invasive breast carcinoma (n=2742) were reviewed to determine the diagnoses, including histologic type, grade, presence of lymphovascular invasion (LVI), and extent of RC. No differences were found in the extent of RC between corresponding core needle biopsy and surgical samples. Extent of RC showed a significant correlation with tumor size, grade, LVI, and nodal metastasis in both core needle biopsy and surgical specimens. These associations remained significant in subset analyses of small (≤1 cm), node-negative and node-positive tumors. Extensive RC predicted poor recurrence-free (P<0.0001) and overall (P<0.0001) survival and remained significant in subset analyses of node-negative (P=0.0015 and 0.0021, respectively) and node-positive (P=0.0039 and 0.0214, respectively) cases. Carcinomas without LVI but extensive RC were associated with better outcome than carcinomas with LVI but worse than those without LVI and low RC. This prospective study confirms that the presence of extensive RC in invasive breast carcinomas correlates with aggressive tumor features and lymphatic tumor spread. Extensive RC appears to be an independent factor predictive of poor outcome in node-negative and node-positive disease. Our results support the hypothesis that RCs are the morphologic reflection of biological changes in tumor cells playing a role in lymphatic tumor spread and likely represent an early stage of LVI with similar clinical implications.

Gastric intramucosal adenocarcinoma with an invasive micropapillary carcinoma component

A 70-year-old woman was referred to our hospital because of early gastric cancer (lesser curvature of the antrum, 0-IIc, tub1, 15 mm) and underwent endoscopic submucosal dissection. Microscopically, the lesion was found to be confined to the mucosa, and predominantly composed of well-differentiated tubular adenocarcinoma with a micropapillary component. On immunohistochemical examination, the characteristic "inside-out pattern" of the micropapillary component was observed; thus, we diagnosed the lesion as gastric cancer with a micropapillary component. Invasive micropapillary carcinoma is a rare subtype of gastric carcinoma, and, to our knowledge, this is the first case of invasive micropapillary carcinoma of the stomach confined to the mucosa.

Micropapillary pattern and poorly differentiated clusters represent the same biological phenomenon in colorectal cancer: a proposal for a change in terminology

OBJECTIVES

Colorectal carcinomas (CRCs) with a micropapillary pattern and those showing high counts of poorly differentiated clusters (PDCs) are characterized by a higher probability to develop nodal metastases and have a worse prognosis. In light of the morphologic similarity to the micropapillary component, we aimed to verify whether PDCs also display an inverted secretory pattern.

METHODS

The immunohistochemical expression of MUC1 and E-cadherin was assessed in a cohort of CRCs with PDCs and compared with that observed in CRCs without PDCs.

RESULTS

PDCs in our cases always displayed an inverted MUC1 pattern. In addition, we found abnormal (lost or cytoplasmic) expression of E-cadherin in PDCs.

CONCLUSIONS

The altered expression of MUC1 and E-cadherin may account for the aggressive behavior and higher metastatic potential of CRCs with high PDC counts and indicate an epithelial-mesenchymal transition. Our findings suggest that regardless of the morphologic aspect, PDCs and the micropapillary component may reflect the same biological phenomenon in CRCs. Thus, we wonder whether the micropapillary areas should be considered a variant of CRCs or more objectively counted as PDCs to predict prognosis. We also believe that the term PDC better describes the biological phenomena underlying this peculiar morphologic aspect in comparison with the misnomer micropapillary.

Invasive micropapillary carcinoma: A distinct type of adenocarcinomas in the gastrointestinal tract

Invasive micropapillary carcinoma (IMPC) is a rare histological type of tumor, first described in invasive ductal breast cancer, than in malignancies in other organs such as lungs, urinary bladder, ovaries or salivary glands. Recent literature data shows that this histological lesion has also been found in cancers of the gastrointestinal system. The micropapillary components are clusters of neoplastic cells that closely adhere to each other and are located in distinct empty spaces. Moreover, clusters of neoplastic cells do not have a fibrous-vascular core. The IMPC cells show reverse polarity resulting in typical ‘’inside-out’’ structures that determines secretary properties, disturbs adhesion and conditions grade of malignancy in gastrointestinal (GI) tract. Invasive micropapillary carcinoma in this location is associated with metastases to local lymph nodes and lymphovascular invasion. IMPC can be a prognostic factor for patients with cancers of the stomach, pancreas and with colorectal cancer since it is related with disease-free and overall survival. The purpose of this review is to present the characterization of invasive micropapillary carcinoma in colon, rectum, stomach and others site of GI tract, and to determine the immunohistological indentification of IMPC in those localization.

Poorly differentiated clusters (PDCs) as a novel histological predictor of nodal metastases in pT1 colorectal cancer

The practical use of histological factors such as submucosal (SM) invasion depth, poor differentiation, presence of lymphovascular invasion (LVI) and tumour budding to establish the risk of nodal dissemination in pT1 colorectal cancer (CRC) is limited by their low standardization and high inter-observer variability. It was recently suggested that the presence in CRC histological sections of poorly differentiated clusters (PDCs), defined as ≥5 cancer cells with no gland formation, may predict the metastatic potential of CRC. In addition, PDC assessment was shown to be more reproducible than the evaluation of the other aforementioned histological predictors. Hence, in this study, we investigated and compared the predictive value of PDC and other histological parameters on the risk of nodal involvement in pT1 CRC. The presence of PDC, SM invasion depth ≥1,000 μm and LVI was significantly associated with N+ status in pT1 CRC (P < 0.0001). Among these parameters, SM invasion depth had the highest sensitivity to identify N+ pT1 CRC but with the lowest specificity. When the analysis was restricted to CRCs with SM invasion depth ≥1,000 μm, the presence of PDC was the only independent risk factor for nodal metastases and allowed the identification of 87.5 % of N+ cancers. In conclusion, in this study, we demonstrate that the presence of PDC is associated with the metastatic potential of pT1 CRC. The combination of this parameter with SM invasion depth may allow identifying most of the pT1 CRC with nodal metastases.

Micropapillary pattern at the invasive front and its association with unresectable colorectal carcinomas

Unresectable colorectal carcinomas (CRCs) as considered incurable even if the primary tumors and the metastatic ones can undergo resection are correlated with poor prognosis. We evaluated the association between micropapillary pattern at the invasive front and unresectable CRCs. Thirty-four out of 264 (12.9%) CRC patients with stages III and IV were unresectable cases. The patients with unresectable CRCs had significantly worse survival than those with resectable CRCs (P < 0.001). Micropapillary pattern was evident in 12 (4.5%) out of 264 cases. This pattern was observed in 6 of 34 (17.6%) unresectable CRCs and in 6 of 230 (2.6%) resectable cases (P = 0.002). Unresectable CRCs revealed more frequently deeper invasion (odds ratio (OR), 1.175; 95% confidence interval (CI), 1.113-1.241), lymph node metastasis (OR, 2.356; 95% CI, 1.132-4.905), and presence of micropapillary pattern at the invasive front (OR, 8.000; 95% CI, 2.415-26.504) as compared to resectable cases. By multivariable logistic regression analysis, only micropapillary pattern was shown to be an independent predictor of unresectable CRCs (OR, 9.451; 95% CI, 2.468-36.196; P < 0.001). In conclusion, micropapillary pattern at the invasive front is associated with unresectable CRCs, and detection of it could help identify unresectable CRC cases.

Micropapillary variant of embryonal carcinoma: clinicopathological correlation and histochemical study

Micropapillary pattern of growth (MPG) of carcinoma is a unique morphologic pattern. It is uncommon but a predictor of poor outcome. MPG has not been described in any germ cell tumor, most notably embryonal carcinoma, which may have papillary configuration. In this study, we reviewed 25 primary testicular germ cell tumors (pure or mixed) containing embryonal carcinoma and 2 lymph node metastases with embryonal carcinoma. Five of the 25 primary cases demonstrated MPG. With available clinical information, 3/3 (100%) cases with MPG and 5/12 (42%) cases without MPG showed evidence of metastases. The 2 lymph node metastases contained predominantly MPG. At metastasis, the median tumor size in primary tumors with MPG was significantly smaller than in those without MPG. Reticulum staining was negative in the regions of MPG and positive for other coexisting non-micropapillary growth patterns in all the 6 embryonal carcinomas. In conclusion, we described MPG in embryonal carcinoma. Although limited by the number of cases, our clinicopathological correlation results raised the possible association of the presence of MPG to the high-rate metastasis of embryonal carcinoma, similar to that seen in other carcinomas with MPG. It is therefore of importance to document this variant growth pattern if present in embryonal carcinoma. We also demonstrated that reticulum is a useful negative marker for identification of MPG.

Five-year survival after surgery for invasive micropapillary carcinoma of the stomach

Invasive micropapillary carcinoma (IMPC) of the breast, urinary bladder, ovary, and colon has been reported. However, few reports have described IMPC of the stomach. In addition, IMPC has been described as a histological indicator for lymphatic invasion and nodal metastasis, resulting in poor prognosis. We report a case of 5-year survival after surgery for IPMC of the stomach. A 69-year-old woman was admitted to our hospital with symptoms of upper abdominal pain. Upper gastrointestinal endoscopy revealed a tumor at the antrum of the stomach. Histological examination of the biopsy specimen indicated poorly differentiated adenocarcinoma. The patient underwent distal gastrectomy with lymph node dissection. Microscopic examination of the specimen revealed that the tumor consisted of an invasive micropapillary component. Carcinoma cell clusters were floating in the clear spaces. The patient recovered uneventfully and remains alive without recurrence 5 years after surgery.

Immunohistochemical analysis of invasive micropapillary carcinoma pattern in four cases of gastric cancer

Gastric cancer with the invasive micropapillary carcinoma (IMPC) pattern has been reported to be a variant with poor prognosis and rapid progression. To the best of our knowledge, only 4 cases of gastric cancer from Japan and 11 cases from Korea have been reported to contain the IMPC pattern. In the present study, 4 cases of gastric cancer containing the IMPC pattern from 2 Japanese men and 2 Japanese women are reported. The cancer tissues, including a recurrent lesion in 1 case and lymph node metastases in 2 other cases, were examined immunohistochemically to identify suitable markers for demonstrating the peculiar "inside out" pattern of IMPC and for analyzing HER2 expression. A characteristic IMPC pattern occupied more than 10% of each cancer tissue in these 4 cases. Lymphatic invasions were very often detected; in fact, lymph node metastases were detected in 3 out of 4 cases. The unique "inside out" pattern in IMPC was clearly revealed in all cases by staining with antibodies to both epithelial membrane antigen (EMA) and KL-6, but not with an antibody to CD10. HER2 was positive in 3 of 4 cases with the IMPC pattern, including cases with a recurrent lesion or lymph node metastases. Fluorescence in situ hybridization (FISH) analyses disclosed positive results in case 1, and case 3 including lymph node metastatic foci. Highest FISH titer was 6.8 in case 1, revealing marked amplification of HER-2 gene. Four cases of gastric cancer with the IMPC pattern were reported. EMA and KL-6, but not CD10, were particularly useful markers for visualizing the characteristic "inside out" pattern of the IMPC pattern in stomach cancers, similar to the markers for breast and urinary bladder cancers.

Colonic micropapillary carcinoma, a recently recognized subtype associated with histological adverse factors: clinicopathological analysis of 15 cases

AIM

Micropapillary carcinoma (MPC) is regarded as an aggressive variant of adenocarcinoma in any location. The reported proportion of a micropapillary carcinoma component in an entire tumour ranges from 5 to 95% and only one case of pure MPC has been reported. To date, approximately 130 cases of MPC in the colorectum have been reported, but it is likely that this small number is to some extent due to under-reporting because this pattern is not well recognized by the general pathologist. All previous studies have combined colonic and rectal primary tumours and most have only analysed patients with clinical Stages I or II.

METHOD

We analysed 15 cases of MPC of the colon alone, diagnosed in our institution, and compared them with 105 conventional carcinomas of the colon.

RESULTS

An MPC component was present in 10% of all colonic carcinomas. These tumours presented at a median age of 56 years, and all were of American Joint Committee on Cancer Stages III and IV. Subserosal tissue invasion was present in every case, 60% had more than four positive lymph nodes, 60% were accompanied by poorly differentiated conventional carcinoma, 40% had had an incomplete resection and a third demonstrated lymphovascular invasion. Despite these adverse prognostic factors, tumours containing MPC showed the same survival, stage by stage, as conventional adenocarcinoma in multivariate analysis, although 3-year survival (81.7%vs 87.3%, P=0.035) was worse on univariate analysis.

CONCLUSION

The histopathologist should be aware of the possibility of MPC. Three-year survival is worse than in patients with conventional colonic carcinomas in Stage III.

Immunohistochemistry of colorectal carcinoma: current practice and evolving applications

The relatively high incidence of adenocarcinoma of the colon and rectum (colorectal carcinoma) in the general population makes its pathologic diagnosis one of the more frequent exercises in anatomical pathology. Although typically mundane in the primary setting, the correct identification of metastatic colorectal carcinoma or exclusion of metastatic disease from carcinoma arising in other anatomical foci can be problematic. The advent of targeted therapies and refinement of more traditional cytotoxic chemotherapeutic regimens mandates not only a more confident appraisal of site of origin but also assessment of those tumor-specific features that may alter therapeutic decisions. Despite the exponential increase in our understanding of the molecular pathogenesis of colorectal carcinoma, immunohistochemistry remains the foundation for resolution of these problematic cases and the number of antibodies available to the practicing pathologist continues to expand at a steady rate. In some cases, immunohistochemistry may also provide valuable prognostic information, either independently or as a surrogate marker for a specific route of carcinogenesis such as microsatellite instability. This review will focus on the use of new and more established immunohistochemistry markers in the diagnosis of colorectal carcinoma, with an emphasis on aberrant staining patterns of the various colorectal carcinoma subtypes as well as the utility of these markers in specific differential diagnostic settings.

Clinicopathological features of stomach cancer with invasive micropapillary component

BACKGROUND

Invasive micropapillary carcinoma has been recognized as a rare disease entity with aggressive tumor behavior. However, few reports have described invasive micropapillary carcinoma in the gastrointestinal tract, particularly its involvement in gastric cancer.

METHODS

We retrospectively analyzed 930 patients diagnosed with gastric cancer who underwent gastrectomy, and we then histopathologically evaluated the existence of a regional invasive micropapillary component. Clinicopathological features were investigated in patients with an invasive micropapillary component and compared with such features in 100 patients with gastric adenocarcinoma, selected as stage-matched controls, who underwent gastrectomy during the same period.

RESULTS

Of the 930 patients, 14 were histopathologically diagnosed with gastric cancer with a regional invasive micropapillary component. There were no significant differences in age, gender, tumor location, macroscopic type, or type of surgery between patients with an invasive micropapillary component and the pT-matched controls. Histopathologically, significant differences were observed in lymphatic infiltration, venous invasion, the percentage of cases with lymph node metastasis, and the median number of metastatic lymph nodes. The three-year disease-free and overall survival rates of patients with an invasive micropapillary component were 40.5 and 59.3%, respectively, compared with those for the stage-matched controls, which were 72.6 and 80.6%, respectively (p = 0.02 and 0.07).

CONCLUSIONS

Patients with gastric cancer with a regional invasive micropapillary component showed marked cancer infiltration in the lymphatic pathway and poor prognosis after gastrectomy.

Stromal micropapillary pattern predominant lung adenocarcinoma--a report of two cases

Generally, adenocarcinomas with micropapillary pattern, featuring small papillary tufts lacking a central fibrovascular core, are thought to have poor prognosis. This pattern has been described in various organs. However, tumor cells with micropapillary pattern of lung adenocarcinoma are more often seen to float within alveolar spaces (aerogenous micropapillary pattern, AMP) than in fibrotic stroma like other organs (stromal micropapillary pattern, SMP) and SMP predominant lung adenocarcinoma (SMPPLA) has not been well described yet. We presented two cases of SMPPLA which were found in the last four years. Both the cases showed more than 50% of SMP in the tumor area. The majority of the stromal micropapillary clusters expressed MUC1 and epithelial membrane antigen along the outer surface of cell membrane. On the other hand, connective tissues surrounding stromal micropapillary clusters showed no reactivity for epithelial markers (thyroid transcription factor-1 and cytokeratin) or endothelial marker (D2-40 and CD34). It means clusters of SMP do not exist within air space or lymphatic or vessel lumens. The tumors with SMP often presented lymphatic permeation and vessel invasion, and intriguingly, one of the two cases showed metastasis to the mediastinal lymph node. Additionally, both the cases showed EGFR point mutations of exon 21. These results suggest that SMPPLA might be associated with poor prognosis and effective for EGFR tyrosine kinase inhibitors.

Pleomorphic epithelioid diffuse malignant pleural mesothelioma: a clinicopathological review and conceptual proposal to reclassify as biphasic or sarcomatoid mesothelioma

INTRODUCTION

In patients with epithelioid diffuse malignant pleural mesothelioma (DMPM), clinical stage is the current primary prognostic factor. We sought to investigate whether histologic subtyping can prognostically stratify patients with epithelioid DMPM.

METHODS

Hematoxylin and eosin-stained slides of 232 patients with epithelioid DMPM (14 stage I, 54 stage II, 130 stage III, and 34 stage IV) from a single institution were reviewed. We classified the tumors into five subtypes, according to the predominant histological pattern: trabecular, tubulopapillary, micropapillary, solid, and pleomorphic (≥10% of tumor).

RESULTS

Median overall survival (OS) of all patients with epithelioid DMPM was 16.2 months. Patients with pleomorphic subtype (n = 34) had the worst median OS (8.1 months), followed by solid (n = 89, 13.7 months), micropapillary (n = 20, 15.8 months), tubulopapillary (n = 51, 17.9 months), and trabecular (n = 38, 24.9 months). The pleomorphic subtype was associated with lymphatic and vascular invasion (p < 0.001). The micropapillary subtype was associated with lymphatic invasion (p < 0.001). In univariate analyses, pleomorphic subtype was significantly associated with poor OS (p = 0.003). The pleomorphic subtype showed no significant difference on OS compared with biphasic and sarcomatoid DMPM. In a multivariate analysis, the pleomorphic subtype was an independent predictor of poor OS (p = 0.031). In patients who underwent R1 resection, pleomorphic subtype had the shortest median time to recurrence (13.7 months).

CONCLUSION

Our finding that the pleomorphic subtype is a predictor of aggressive behavior in epithelioid DMPM with no survival difference from biphasic or sarcomatoid DMPM suggests that it may be best regarded as a sarcomatoid pattern rather than a subtype of epithelioid DMPM.