Micropapillary carcinoma of stomach: a clinicopathologic and immunohistochemical study of 11 cases. Am J Surg Pathol. 2010;34:1139-1146. [PMID: 20661012 DOI: 10.1097/pas.0b013e3181e7043b]

Unusual or Uncommon Histology of Gastric Cancer

This review comprehensively examines the diverse spectrum of gastric cancers, focusing on unusual or uncommon histology that presents significant diagnostic and therapeutic challenges. While the predominant form, tubular adenocarcinoma, is well-characterized, this review focuses on lesser-known variants, including papillary adenocarcinoma, micropapillary carcinoma, adenosquamous carcinoma, squamous cell carcinoma (SCC), hepatoid adenocarcinoma, gastric choriocarcinoma, gastric carcinoma with lymphoid stroma, carcinosarcoma, gastroblastoma, parietal cell carcinoma, oncocytic adenocarcinoma, Paneth cell carcinoma, gastric adenocarcinoma of the fundic gland type, undifferentiated carcinoma, and extremely well-differentiated adenocarcinoma. Although these diseases have different nomenclatures characterized by distinct histopathological features, these phenotypes often overlap, making it difficult to draw clear boundaries. Furthermore, the number of cases was limited, and the unique histopathological nature and potential pathogenic mechanisms were not well defined. This review highlights the importance of understanding these rare variants for accurate diagnosis, effective treatment planning, and improving patient outcomes. This review emphasizes the need for ongoing research and case studies to enhance our knowledge of these uncommon forms of gastric cancer, which will ultimately contribute to more effective treatments and better prognostic assessments. This review aimed to broaden the pathological narrative by acknowledging and addressing the intricacies of all cancer types, regardless of their rarity, to advance patient care and improve prognosis.

A Standardized Pathology Report for Gastric Cancer: 2nd Edition

The first edition of 'A Standardized Pathology Report for Gastric Cancer' was initiated by the Gastrointestinal Pathology Study Group of the Korean Society of Pathologists and published 17 years ago. Since then, significant advances have been made in the pathologic diagnosis, molecular genetics, and management of gastric cancer (GC). To reflect those changes, a committee for publishing a second edition of the report was formed within the Gastrointestinal Pathology Study Group of the Korean Society of Pathologists. This second edition consists of two parts: standard data elements and conditional data elements. The standard data elements contain the basic pathologic findings and items necessary to predict the prognosis of GC patients, and they are adequate for routine surgical pathology service. Other diagnostic and prognostic factors relevant to adjuvant therapy, including molecular biomarkers, are classified as conditional data elements to allow each pathologist to selectively choose items appropriate to the environment in their institution. We trust that the standardized pathology report will be helpful for GC diagnosis and facilitate large-scale multidisciplinary collaborative studies.

Precancerous lesions of the stomach, gastric cancer and hereditary gastric cancer syndromes

Gastric cancer accounts for about 6% of cancers worldwide, being the fifth most frequently diagnosed malignancy and the third leading cause of cancer related death. Gastric carcinogenesis is a multistep and multifactorial process and is the result of the complex interplay between genetic susceptibility and environmental factors. The identification of predisposing conditions and of precancerous lesions is the basis for screening programs and early stage treatment. Furthermore, although most gastric cancers are sporadic, familial clustering is observed in up to 10% of patients. Among them, hereditary cases, related to known cancer susceptibility syndromes and/or genetic causes are thought to account for 1-3% of all gastric cancers. The pathology report of gastric resections specimens therefore requires a standardized approach as well as in depth knowledge of prognostic and treatment associated factors.

Gastrectomy for invasive micropapillary carcinoma is associated with poorer disease-free and disease-specific survival

BACKGROUND

Invasive micropapillary carcinoma (IMPC) is a relatively rare subtype of gastric adenocarcinoma and has aggressive histopathologic characteristics, including lymphatic and vascular invasion. However, the associated long-term survival outcomes remain unclear. This study aimed to compare the clinicopathological characteristics and prognosis of gastric adenocarcinoma with and without IMPC using propensity score-matched (PSM) analysis.

METHODS

Patients with gastric adenocarcinoma who underwent gastrectomy between 2006 and 2015 were included in the analysis. PSM analysis was performed to compensate for the background heterogeneity between the groups. The primary endpoint was disease-free survival (DFS) after gastrectomy, and the secondary endpoints were disease-specific survival (DSS) and recurrence pattern.

RESULTS

Of 882 patients who underwent gastrectomy for gastric adenocarcinoma, with a follow-up duration greater than 36 months, 35 were diagnosed as having gastric adenocarcinoma with IMPC. After PSM, 70 patients, including 35 with IMPC and 35 without IMPC, were selected. Gastric adenocarcinoma with IMPC is characterized by lymphatic invasion (94% versus 69%, p = 0.012). Patients with IMPC had significantly poorer DFS than those without IMPC, with 3-year DFS rates of 62.2% and 93.4% (p = 0.003), respectively. Furthermore, a significant difference was also observed in DSS (p = 0.016); patients with IMPC more frequently developed liver metastasis (20%) than those without IMPC (3%, p = 0.006).

CONCLUSIONS

Resected gastric carcinoma with IMPC was associated with poorer DFS and DSS; furthermore, an increased rate of lymphatic invasion and liver metastasis was noted than in cases without IMPC.

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.

Invasive Micropapillary Carcinoma of the Uterine Cervix: Case Report of a Rare Entity

Invasive micropapillary carcinoma (IMPC) is a rare subtype of adenocarcinoma found in many organs. Only 1 case of IMPC of the uterine cervix has been reported. We report a rare case of IMPC in the uterine cervix. A 61-yr-old woman presented to our hospital for vaginal bleeding and abdominal pain. A papillary tumor was found in the uterine cervix. Cervical cytology revealed abnormal cells suggesting carcinoma in situ and adenocarcinoma. A follow up biopsy revealed adenocarcinoma. She underwent radical hysterectomy and bilateral adnexectomy. Histologically, carcinoma in situ and IMPC were found in the uterine cervix. Lymphatic infiltration was present in the cerix and in the right cardinal ligament. A pelvic lymph node metastasis was also identified. Clinical FIGO stage was IIb and pathologic stage was pT2bN1M0. Postoperative positron emission tomography-computed tomography revealed paraaortic lymph node metastasis. She is alive with disease 2 yr 9 mo after surgery. Positive p16 immunostaining and high-risk human papilloma virus in situ hybridization revealed human papilloma virus infection. Interleukin-17 was expressed in the tumor cells which might be related to the extensive neutrophilic infiltration and tumor progression. This is the first case report in which interleukin-17 expression is observed in the tumor cells of IMPC.

HER2 is frequently overexpressed in hepatoid adenocarcinoma and gastric carcinoma with enteroblastic differentiation: a comparison of 35 cases to 334 gastric carcinomas of other histological types

AIMS

α-Fetoprotein (AFP)-producing gastric carcinoma (AFPGC) is one of the most aggressive GC subtypes. Frequent expression of human epidermal growth factor receptor 2 (HER2) has previously been reported in hepatoid adenocarcinoma (HAC), a major histological subtype of AFPGC originating from common-type GC (CGC). However, HER2 expression levels in other AFPGC histological subtypes are unknown. In this study, we analysed HER2 expression in GCs with primitive phenotypes in addition to HAC.

METHODS

HER2 expression was evaluated in representative complete sections from 16 HACs, 19 GCs with enteroblastic differentiation (GCEDs) and 334 GCs of other histological types as controls. The Ruschoff/Hofmann method was used to score HER2 immunohistochemistry. Samples with a HER2 score of 2+ were further assessed using fluorescence in situ hybridisation. Oncofetal protein (OFP) expression in HAC and GCED was tested via immunohistochemical staining for AFP, glypican 3 and Sal-like protein 4.

RESULTS

Thirty of 35 HAC/GCED cases comprised more than two histological patterns. The HER2 positivity rates of each histological component in the HACs/GCEDs were 25.0% for HAC (n=16), 34.6% for GCED (n=26) and 48.1% for CGC (n=27), which were higher than those of the control group (13.8%). Additionally, the majority of CGC components in HACs/GCEDs were positive for OFP (88.9%).

CONCLUSIONS

HER2 is frequently overexpressed not only in HAC but also in GCED and CGC components of HACs/GCEDs, which suggests an association between HER2 and OFP expression. Moreover, our findings suggest that HER2-positive CGC has a higher risk of progression to HAC/GCED than HER2-negative GC.

Practical Points in Gastric Pathology

CONTEXT

-The diagnosis of gastric epithelial lesions is difficult in clinical practice, even with the recent developments and advances in endoscopic modalities, owing to the diverse morphologic features of the lesions, lack of standardized diagnostic criteria, and the high intraobserver and interobserver variabilities in the nonneoplastic (regenerative)-neoplastic spectrum.

OBJECTIVE

-To provide an overview of the current concepts and unresolved issues surrounding the diagnosis of diseases in the nonneoplastic-neoplastic spectrum, and to discuss some noteworthy properties and histologic features of gastric epithelial lesions.

DATA SOURCES

-A comprehensive assessment of the medical literature on gastric epithelial lesions was performed; we also interjected our own experiences into the discussion. Sources included original studies, review articles, and textbooks related to the field.

CONCLUSIONS

-Our literature review revealed that clear cell changes and micropapillary carcinoma components in gastric carcinomas are associated with poor clinical outcomes and should hence be included in pathologic reports. Moreover, we suggest a stepwise biopsy-endoscopic resection modality for the diagnosis of borderline neoplasia-nonneoplasia cases.

HER2 heterogeneity in gastric/gastroesophageal cancers: From benchside to practice

HER2 is overexpressed in approximately 10%-20% of gastric and gastroesophageal junction carcinomas. In these types of cancer, accurate assessment of HER2 status is mandatory, for selecting patients who may benefit from targeted therapies with anti-HER2 drugs such as Trastuzumab. This manuscript focuses on HER2 in gastric carcinogenesis, on optimal evaluation of HER2 and on the possible causes which may contribute to inaccurate HER2 evaluation. Similarly to breast cancer HER2 evaluation, standardization of HER2 testing in gastric cancer is necessary in diagnostic practice. The three principle aspects which require consideration are: (1) the choice of sample with regards to cancer morphology - intestinal vs diffuse areas; (2) the choice of scoring criteria - use of HER2 scoring criteria specific for gastric cancer; and (3) the choice of HER2 evaluation methods - use of an algorithm in which both immunohistochemistry and in situ hybridization play a role. Problematic issues include: (1) pre-analytic variables with particular emphasis on fixation; (2) recommended methodology for HER2 assessment (immunohistochemistry vs in situ hybridization); (3) HER2 heterogeneity both within the primary tumor and between primary tumor and metastases; (4) reliability of biopsies in HER 2 evaluation; and (5) quantity of sample (FFPE blocks from surgical specimens or endoscopic biopsies) necessary for an adequate assessment.

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.

Differences in Clinicopathology of Early Gastric Carcinoma between Proximal and Distal Location in 438 Chinese Patients

Early gastric carcinoma (EGC) in Chinese patients remains poorly understood and endoscopic therapy has not been well established. Here, we compared endoscopic and clinicopathologic features between early proximal gastric carcinoma (PGC, n = 131) and distal gastric carcinoma (DGC, n = 307) in consecutive 438 EGCs diagnosed with the WHO criteria. By endoscopy, PGCs showed protruding and elevated patterns in 61.9%, while depressed and excavated patterns in 33.6%, which were significantly different from those (32.6% and 64.5%) in DGCs. PGCs were significantly smaller (1.9 cm in average, versus 2.2 cm in DGCs), invaded deeper (22.9% into SM2, versus 13% in DGCs), but had fewer (2.9%, versus 16.7% in DGCs) lymph node metastases. Papillary adenocarcinoma was significantly more frequent (32.1%, versus 12.1% in DGCs), as were mucinous and neuroendocrine carcinomas, carcinoma with lymphoid stroma (6.9%, versus 1.6% in DGCs); but poorly cohesive carcinoma was significantly less frequent (5.3%, versus 35.8% in DGCs). The overall 5-year survival rate was 92.9% in EGCs, and PGC patients showed shorter (42.4 months, versus 48.3 in DGCs) survival. Papillary and micropapillary adenocarcinomas and nodal metastasis were independent risk factors for worse survival in EGCs. EGCs in Chinese were heterogeneous with significant differences in endoscopy and clinicopathology between PGC and DGC.

Gastric carcinoma with an invasive micropapillary carcinoma component showing HER2 gene amplification and CD10 expression: a case report and review of the literature

An 81-year-old man was referred to our hospital because gastric cancer was detected on screening esophagogastroduodenoscopy. Surgical resection of the tumor was performed. It was 25 × 20 mm in size and swollen lymph nodes were present nearby. Lymphadenectomy was also performed. Histopathologically, the tumor reached the proper muscle layer via venous invasion. There were three components that constituted the tumor, that is, 40% of mass was invasive micropapillary carcinoma (IMPC), 40% was papillary adenocarcinoma and 20% tubular adenocarcinoma. Vascular invasion was prominent. Immunohistochemistry revealed that the tumor showed an entirely intestinal mucin phenotype, being positive only for CD10 and negative for MUC2, MUC5AC, and MUC6. HER2 staining score ranged from 2+ to 3+, depending on the components described above. HER2 gene amplification was present in all the components according to dual-color in situ hybridization. The metastatic lymph nodes were similar to the primary site in morphology and immunohistochemistry, but HER2 amplification was higher in the lymph nodes. The IMPC component with HER2 amplification is rarely seen and its positivity for CD10 is an unexpected finding for gastric IMPC. Hence, this is a highly unusual case judging by the literature; further studies are needed to clarify the nature of gastric 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.

HER2 testing in gastric and gastroesophageal adenocarcinomas

The human epidermal growth factor receptor 2 (HER2) is overexpressed in 10% to 35% of gastric and gastroesophageal junction (GEJ) adenocarcinomas. In 2010, the phase III Trastuzumab for Gastric Cancer (ToGA) trial showed that addition of the anti-HER2 monoclonal antibody trastuzumab to chemotherapy significantly improved survival of patients with advanced or metastatic tumors that were positive for HER2 overexpression. As a result, HER2 testing is now recommended for all patients with advanced or metastatic disease, although there is still some debate as to the optimal methods of assessment. HER2 expression in gastric and GEJ tumors shows several differences compared with breast tumors and, for this reason, the proposed criteria for scoring HER2 expression in biopsies and resections of gastric and GEJ carcinomas differ from those used in breast carcinomas. This review discusses what is currently known about the patterns of HER2 expression in gastric and GEJ adenocarcinomas, summarizes the findings of the ToGA trial and its clinical implications, and provides an overview of the recommended guidelines for the most accurate evaluation of HER2 status in gastric and GEJ cancer.

Micropapillary component in gastric adenocarcinoma: an aggressive variant associated with poor prognosis

BACKGROUND

Adenocarcinomas with a micropapillary component (MPC) have been described as an unusual morphological variant in various organs. However, few reports have described MPCs in gastric carcinomas, and the clinicopathological features of MPC are unclear.

METHODS

Immunohistochemistry was used to detect the expression of epithelial membrane antigen, CK7, CK20, p53, epidermal growth factor receptor, β-catenin, c-erbB-2, and Ki-67. Correlation of the MPC to tumor stage, lymph node metastasis, and lymphovascular invasion was performed using Fisher's exact test. Kaplan-Meier estimates were used to analyze overall survival.

RESULTS

Immunohistochemical staining demonstrated that micropapillary and conventional gastric carcinomas showed similar positivity rates for all markers. However, aberrant expression of E-cadherin was detected in the tumors with MPCs without immunoreactivity in the stroma face. Epithelial membrane antigen showed the characteristic inside-out staining pattern of MPCs. Lymphatic invasion (P = 0.003), venous invasion (P = 0.017), lymph node metastasis (P = 0.014), and tumor stage (P = 0.022) were significantly increased in patients with MPCs when compared with conventional adenocarcinomas. MPC subtype II had a significantly higher frequency of lymph node metastasis than subtype I (P = 0.014). However, the proportion of MPC was not associated with lymph node metastases (P = 0.136). Overall survival of patients with an MPC was significantly shorter than that of patients with conventional adenocarcinomas (P = 0.031). In addition, overall survival was significantly lower in patients with a subtype II MPC growth pattern than in those with subtype I MPC in gastric carcinomas (P = 0.040).

CONCLUSION

Gastric adenocarcinomas with MPC appear to be an aggressive variant associated with a poor prognosis. MPCs occurring in gastric adenocarcinomas should be included in surgical pathology reports, even if the proportion of MPC in the lesions is very low in the lesion.

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.

Gastric Invasive Micropapillary Carcinoma with Intestinal Phenotypes Harboring a TP53 R175H Mutation

We report a case of gastric invasive micropapillary carcinoma (IMPC) in an 86-year-old female patient. She was admitted to our hospital with a chief complaint of bloody emesis. Upper gastrointestinal endoscopy found a gastric adenocarcinoma at the antrum. The biopsy specimens showed moderately differentiated adenocarcinoma with invasive small tumor nests. Distal gastrectomy with systematic lymph node dissection demonstrated that the tumor had IMPC through a pathological examination. Despite the depth of tumor invasion (the submucosa), extensive lymph node metastases were observed. Anti-D2-40 immunostaining revealed numerous infiltrating tumor cell nests in the lymphatic vessels, which could explain subsequent multiple lymph node metastases. The adenocarcinoma showed intestinal phenotypes by several immunohistochemical studies. One of these antibodies (CD10) clearly demonstrated the inverted apical-basal (inside-out) pattern of IMPC, whereas it showed an ordinary pattern in intestinal metaplasia adjacent to the tumor. Furthermore, genetic analysis by direct sequencing revealed a point mutation in the exon 5 of TP53 in the tumor. The mutation presumably harbors a missense mutation from Arg to His at the codon 175 (R175H). R175H has been previously described as a ‘gain-of-function’ mutation with a high invasive or metastatic potential in several types of cancers. In summary, this is one of the first reported cases of gastric IMPC with intestinal phenotypes harboring a TP53 R175H mutation in the literature.

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.

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.

HER2/neu gene amplification and protein overexpression in gastric and gastroesophageal junction adenocarcinoma: a review of histopathology, diagnostic testing, and clinical implications

Amplification of the human epidermal growth factor receptor 2/neu (HER2/neu) gene and overexpression of the HER2 protein (HER2) have been shown to occur in gastric and gastroesophageal junction adenocarcinoma in a number of studies. With a dismal survival rate, patients with these cancers stand to benefit from the identification of possible molecular targets such as HER2 for both prognostic and therapeutic purposes. Although these and other carcinomas that overexpress HER2 may have a poorer prognosis and exhibit resistance to conventional chemotherapy, they have also recently been shown to respond to targeted therapy with the anti-HER2 antibody trastuzumab. Here, we briefly review the molecular biology, histopathology, diagnostic techniques, and interpretation, as well as the clinical implications, of HER2 amplification/overexpression in gastric and gastroesophageal adenocarcinoma.

Gastric cancer: Classification, histology and application of molecular pathology

Gastric cancer remains one of the deadly diseases with poor prognosis. New classification of gastric cancers based on histologic features, genotypes and molecular phenotypes helps better understand the characteristics of each subtype, and improve early diagnosis, prevention and treatment. The objective of this article is to review the new classification of gastric cancers and the up-to-date guidance in the application of molecular testing.

Gastric carcinoma with invasive micropapillary pattern and its association with lymph node metastasis

AIMS

This study aimed to characterize the clinicopathological features of invasive micropapillary carcinoma (IMPC) of the stomach.

METHODS AND RESULTS

Seventeen cases of gastric IMPC were identified from histological reviews of 1178 consecutive cases. IMPC components occupied 10-90% of the entire tumours. Fifteen tumours showed invasion into the muscularis propria or deeper, whereas two tumours were limited to the submucosa. All 17 cases were associated with tubular or papillary adenocarcinoma. Lymphatic and venous invasion were identified more frequently in cases with IMPC components than in those without (P = 0.0023 and P = 0.0009, respectively). Nodal metastases were identified in 14 of 17 (82%) cases with IMPC components, whereas they were detected in 540 of 1161 (47%) cases with no IMPC components (P = 0.0053). Multivariate analysis demonstrated that the presence of IMPC was an independent predictor of nodal metastasis.

CONCLUSIONS

Conservative treatments, such as endoscopic resection, should not be used for gastric carcinoma with IMPC components, as these cases are associated with a high propensity for lymphovascular invasion and nodal metastasis.

[Pathology of endoscopic submucosal dissection; how do we interpret?]

It is widely accepted that endoscopic submucosal dissection (ESD) is an important treatment option for cases of early gastric carcinoma where the probability of lymph node metastasis is very low. The resected ESD specimens are carefully examined by serial sections at 2 mm intervals, and if pathology reveals submucosal invasion more than 500 μm and/or lymphovascular invasion, or if the resection margin is involved by the tumor, surgery is recommended. In this point of view, thorough pathologic examination and reporting the accurate pathologic diagnosis of ESD specimen is very important. The diagnostic approach and pitfalls in the diagnosis of ESD specimen are reviewed.