Micropapillary pattern: a distinct pathological marker to subclassify tumours with a significantly poor prognosis within small peripheral lung adenocarcinoma (<=20 mm) with mixed bronchioloalveolar and invasive subtypes (Noguchi's type C tumours)

Prognostic significance of micropapillary pattern in lung adenocarcinoma and expression of apoptosis-related markers: caspase-3, bcl-2, and p53

We evaluated the clinicopathological characteristics and prognostic significance of lung adenocarcinoma with micropapillary pattern (MPP) and analyzed the expression of apoptosis-related markers: caspase-3, bcl-2, and p53. A series of 166 lung adenocarcinoma that had been surgically resected between 2004 and 2009 were reviewed. Histopathologic patterns, presence of tumor necrosis, mitosis, lymphovascular and perineural invasion, the status of pleura, and tumor differentiation were examined. Of the 166 patients; 71 were stage I, 35 stage II, 51 stage III, and nine stage IV. Histologically they were divided into two groups: MPP-positive (n = 55) and MPP-negative (n = 111). The following items were significantly more frequent in the MPP positive group: female gender (p = 0.03), lymph node metastasis (p = 0.031), and pleural invasion (p = 0.045). Age, smoking status, tumor stage, lymphatic invasion, perineural invasion, mitotic count, and survival rates had no statistically significant difference between groups (p > 0.05). In MPP positive tumors, visceral pleural invasion was identified significantly more frequent than in MPP negative tumors, at stage I. Tumors with MPP showed elevated expressions of caspase-3 (94.5%), p53 (60%), and bcl-2 (54.5%). In MPP positive group, the expression of these three markers had no statistically significant impact on survival. In whole population, bcl-2 expression was correlated with a better outcome. We conclude that MPP is associated with poor prognostic factors both in early and late stages in lung adenocarcinoma. Bcl-2 provides prognostic information independent from the MPP.

Impact of proposed IASLC/ATS/ERS classification of lung adenocarcinoma: prognostic subgroups and implications for further revision of staging based on analysis of 514 stage I cases

A new lung adenocarcinoma classification is being proposed by the International Association for the Study of Lung Cancer, American Thoracic Society and European Respiratory Society (IASLC/ATS/ERS). This proposal has not yet been tested in clinical datasets to determine whether it defines prognostically significant subgroups of lung adenocarcinoma. In all, 514 patients who had pathological stage I adenocarcinoma of the lung classified according to the Union for International Cancer Control/American Joint Committee on Cancer 7th Edition, and who had undergone a lobectomy with mediastinal lymph node dissection were retrospectively reviewed. Comprehensive histological subtyping was used to estimate the percentage of each histological subtype and to identify the predominant subtype. Tumors were classified according to the proposed new IASLC/ATS/ERS adenocarcinoma classification. Statistical analyses were made including Kaplan-Meier and Cox regression analyses. There were 323 females (63%) and 191 males (37%) with a median age of 69 years (33-89 years) and 298 stage IA and 216 stage IB patients. Three overall prognostic groups were identified: low grade: adenocarcinoma in situ (n=1) and minimally invasive adenocarcinoma (n=8) had 100% 5-year disease-free survival; intermediate grade: non-mucinous lepidic predominant (n=29), papillary predominant (n=143) and acinar predominant (n=232) with 90, 83 and 84% 5-year disease-free survival, respectively; and high grade: invasive mucinous adenocarcinoma (n=13), colloid predominant (n=9), solid predominant (n=67) and micropapillary predominant (n=12), with 75, 7170 and 67%, 5-year disease-free survival, respectively (P<0.001). Among the clinicopathological factors, stage 1B versus 1A (P<0.001), male sex (P<0.008), high histological grade (P<0.001), vascular invasion (P=0.002) and necrosis (P<0.001) were poorer prognostic factors on univariate analysis. Both gross tumor size (P=0.04) and invasive tumor size adjusted by the percentage of lepidic growth (P<0.001) were significantly associated with disease-free survival with a slightly stronger association for the latter. Multivariate analysis showed the prognostic groups of the IASLC/ATS/ERS histological classification (P=0.038), male gender (P=0.007), tumor invasive size (P=0.026) and necrosis (P=0.002) were significant poor prognostic factors. In summary, the proposed IASLC/ATS/ERS classification of lung adenocarcinoma identifies histological categories with prognostic differences that may be helpful in identifying candidates for adjunctive therapy. The slightly stronger association with survival for invasive size versus gross size raises the need for further studies to determine whether this adjustment in measuring tumor size could impact TNM staging for small adenocarcinomas.

[Bronchiolar-alveolar carcinoma: From concept to innovative therapeutic strategies]

Bronchioloalveolar carcinoma (BAC) is a primary pulmonary adenocarcinoma (ADC) developped from the terminal respiratory unit. Its restrictive definition adopted by the 1999 WHO pathological classification needs a complete tumor resection to exclude any signs of histological invasion. Although IIIB-IV tumors were excluded from the strict WHO definition of BAC, the first international workshop on BAC in 2004 had focussed on the need to include in the same spectrum of disease pure BAC and ADC with BAC feature (ADC-WBF). BAC and ADC-WBF affect more frequently women, non-smokers and Asian people than other non-small cell carcinoma. Their predominant lepidic and aerogenous tumor progression results in a frequent pneumonic, multifocal or diffuse presentation and explains why death is more frequently related to bilateral pulmonary involvement than extrathoracic metastasis. Natural history is slower and prognosis better than for other ADC. Within this entity, there are different cytological subtypes: mucinous, non-mucinous and mixed and according to them different clinical and biological phenotypes, with different sensitivity to therapeutic agents. At present, the diagnosis, the staging and the therapeutic strategy does not differ from that of non-small lung carcinoma cells. In localized forms, surgical resection remains the best therapeutic option for localized tumors. In diffuse forms, high frequency of epidermal growth factor receptor (EGFR) expression on tumor cells and its gene amplification and/or mutation as well as a particular sensitivity of this entity to EGFR tyrosine kinase inhibitors offer new strategy of therapeutical management in patients with non-resectable tumor. However, the place of chemotherapy has recently been revisited in this entity known until now as chemoresistant tumors. The results are being evaluated. It is necessary to continue therapeutic trials to determine criteria for choosing a first-line TKI or conventional chemotherapy in that entity. Cytological subtype will probably have an important role to play in this choice.

International association for the study of lung cancer/american thoracic society/european respiratory society international multidisciplinary classification of lung adenocarcinoma

INTRODUCTION

Adenocarcinoma is the most common histologic type of lung cancer. To address advances in oncology, molecular biology, pathology, radiology, and surgery of lung adenocarcinoma, an international multidisciplinary classification was sponsored by the International Association for the Study of Lung Cancer, American Thoracic Society, and European Respiratory Society. This new adenocarcinoma classification is needed to provide uniform terminology and diagnostic criteria, especially for bronchioloalveolar carcinoma (BAC), the overall approach to small nonresection cancer specimens, and for multidisciplinary strategic management of tissue for molecular and immunohistochemical studies.

METHODS

An international core panel of experts representing all three societies was formed with oncologists/pulmonologists, pathologists, radiologists, molecular biologists, and thoracic surgeons. A systematic review was performed under the guidance of the American Thoracic Society Documents Development and Implementation Committee. The search strategy identified 11,368 citations of which 312 articles met specified eligibility criteria and were retrieved for full text review. A series of meetings were held to discuss the development of the new classification, to develop the recommendations, and to write the current document. Recommendations for key questions were graded by strength and quality of the evidence according to the Grades of Recommendation, Assessment, Development, and Evaluation approach.

RESULTS

The classification addresses both resection specimens, and small biopsies and cytology. The terms BAC and mixed subtype adenocarcinoma are no longer used. For resection specimens, new concepts are introduced such as adenocarcinoma in situ (AIS) and minimally invasive adenocarcinoma (MIA) for small solitary adenocarcinomas with either pure lepidic growth (AIS) or predominant lepidic growth with ≤ 5 mm invasion (MIA) to define patients who, if they undergo complete resection, will have 100% or near 100% disease-specific survival, respectively. AIS and MIA are usually nonmucinous but rarely may be mucinous. Invasive adenocarcinomas are classified by predominant pattern after using comprehensive histologic subtyping with lepidic (formerly most mixed subtype tumors with nonmucinous BAC), acinar, papillary, and solid patterns; micropapillary is added as a new histologic subtype. Variants include invasive mucinous adenocarcinoma (formerly mucinous BAC), colloid, fetal, and enteric adenocarcinoma. This classification provides guidance for small biopsies and cytology specimens, as approximately 70% of lung cancers are diagnosed in such samples. Non-small cell lung carcinomas (NSCLCs), in patients with advanced-stage disease, are to be classified into more specific types such as adenocarcinoma or squamous cell carcinoma, whenever possible for several reasons: (1) adenocarcinoma or NSCLC not otherwise specified should be tested for epidermal growth factor receptor (EGFR) mutations as the presence of these mutations is predictive of responsiveness to EGFR tyrosine kinase inhibitors, (2) adenocarcinoma histology is a strong predictor for improved outcome with pemetrexed therapy compared with squamous cell carcinoma, and (3) potential life-threatening hemorrhage may occur in patients with squamous cell carcinoma who receive bevacizumab. If the tumor cannot be classified based on light microscopy alone, special studies such as immunohistochemistry and/or mucin stains should be applied to classify the tumor further. Use of the term NSCLC not otherwise specified should be minimized.

CONCLUSIONS

This new classification strategy is based on a multidisciplinary approach to diagnosis of lung adenocarcinoma that incorporates clinical, molecular, radiologic, and surgical issues, but it is primarily based on histology. This classification is intended to support clinical practice, and research investigation and clinical trials. As EGFR mutation is a validated predictive marker for response and progression-free survival with EGFR tyrosine kinase inhibitors in advanced lung adenocarcinoma, we recommend that patients with advanced adenocarcinomas be tested for EGFR mutation. This has implications for strategic management of tissue, particularly for small biopsies and cytology samples, to maximize high-quality tissue available for molecular studies. Potential impact for tumor, node, and metastasis staging include adjustment of the size T factor according to only the invasive component (1) pathologically in invasive tumors with lepidic areas or (2) radiologically by measuring the solid component of part-solid nodules.

The morphological diversity of small lung adenocarcinoma with mixed subtypes is associated with local invasiveness and prognosis

OBJECTIVE

Under the current World Health Organization (WHO) classification, 'lung adenocarcinoma with mixed subtypes' is the most frequent type, even in small lung adenocarcinoma, with a diameter of 3 cm or less. For this type of lung adenocarcinoma, it has been reported that the high ratio of the peripheral bronchioloalveolar carcinoma (BAC)/lepidic growth (LG) component was a favorable prognostic factor. On the other hand, the central solid components of lung adenocarcinoma with mixed subtypes have not been focused on in the past. In this study, we took note of the histological features in central solid components of lung adenocarcinoma with mixed subtypes and evaluated whether the morphological diversity of these tumors is associated with local invasiveness and prognostic implication.

METHODS

A total of 103 surgically resected peripheral lung adenocarcinomas were reviewed. All the tumors were 3 cm or less in diameter and histologically diagnosed as lung adenocarcinoma with mixed subtypes, containing a BAC/LG component at the peripheral lesion of the tumor. The tumors were classified into two groups, according to the number of histological subtypes in the tumor, using the modified WHO classification (including the micropapillary subtype); group A (n = 76) has two or three histological subtypes, and group B (n = 27) has four or five subtypes in the tumor, respectively. Then, we evaluated the differences in clinicopathological factors and prognosis between these two groups.

RESULTS

Group B was significantly associated with positive lymphatic and vascular invasion, lymph node metastasis, and advanced pathological stage, compared with group A. The 5-year survival rates of all patients were 91.4% for group A and 43.3% for group B, respectively, with a significant difference (p < 0.01). Multivariate analysis showed that the group classification by the number of histological subtypes was an independent prognostic factor in stage IA patients (p < 0.01).

CONCLUSIONS

The morphological diversity of small lung adenocarcinoma with mixed subtypes is an independent prognostic factor and is associated with tumors' local invasiveness and patients' prognosis.

A grading system of lung adenocarcinomas based on histologic pattern is predictive of disease recurrence in stage I tumors

Currently no objective grading system for pulmonary adenocarcinomas exists. To determine whether specific histologic patterns or combinations thereof could be linked to an objective grading system, the histologic patterns in metastatic tumor deposits was compared with the patterns seen in the corresponding 73 primary tumor to determine whether a specific pattern had higher propensity to metastasize. The concordance of the predominant histologic pattern in the primary tumor and the metastases was of 100% for micropapillary, 86% for solid, 42% for acinar, and 23% for papillary types of adenocarcinoma. Informed by these results, a 3-tier grading system based on the histologic subtypes was established. Grade I, a pattern with low metastatic potential (BAC); Grade II, patterns with intermediate metastatic potential (acinar and papillary); and Grade III, patterns with high metastatic potential (solid and micropapillary). These grades were combined into a number of different scoring systems, whose ability to predict recurrence or death from disease was tested in 366 stage 1 adenocarcinomas. A score based on the 2 most predominant grades was able to stratify patients into low-to-high risk for recurrence or death of disease (P=0.001). The 5-years disease-free survival for patients in the highest score group was of 0.73, compared with 0.84 and 0.92 in the intermediate and lowest score groups. Concordance probability estimate was 0.65 (95% confidence interval 0.57-0.73). Therefore, this scoring system provides valuable information in discriminating patients with different risk of disease-recurrence in a highly homogeneous population of patients with stage I cancer.

Portal vein tumor thrombus of liver metastasis from lung cancer

We report a case of liver metastasis of lung carcinoma with portal vein tumor thrombus (PVTT). Although the primary lesion of lung tumor remained unchanged, the patient rapidly developed wide-spread metastases and formed PVTT of liver metastasis. The primary lesion showed features of mixed Clara and bronchial surface epithelial cell component type adenocarcinoma with small foci of micropapillary pattern. Micropapillary pattern was observed in the metastatic lesions in the liver and PVTT. Micropapillary pattern lung adenocarcinoma may develop rapid metastases and cause PVTT associated with liver metastasis. We should perform a detailed examination to establish correct diagnosis.

Is the epidermal growth factor receptor status in lung cancers reflected in clinicopathologic features?

CONTEXT

Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors are molecular-targeted drugs that are innovatively effective for non-small cell lung carcinomas with EGFR mutations. Epidermal growth factor receptor is a transmembrane receptor forming dimers on ligand binding. These then stimulate signals by activating receptor autophosphorylation through tyrosine kinase activity. Autophosphorylation triggers intracellular pathways facilitating malignant conversion. The most clinically advanced EGFR inhibition strategies include small-molecule inhibition of the intracellular tyrosine kinase domain (gefitinib and erlotinib) and monoclonal antibody-mediated blockade of the extracellular ligand-binding domain (cetuximab). Lung cancers with EGFR mutations are prevalent among patients who are female, of Asian ethnicity, and nonsmokers; thus, they can obtain benefit from EGFR tyrosine kinase inhibitors.

OBJECTIVE

To survey histopathologic findings and examine correlations with EGFR mutations. We mainly focused on component cell types (hobnail, columnar, and polygonal) and presence or absence of bronchioloalveolar carcinoma elements and a micropapillary pattern. Although EGFR mutations can be detected by various methods, including polymerase chain reaction-Invader assay or direct sequencing, these are inconvenient.

DATA SOURCES

Review of the published literature.

CONCLUSION

Detailed pathologic examination showed significant genotype-phenotype correlations between EGFR mutations and presence of a bronchioloalveolar carcinoma component, a micropapillary pattern, and the hobnail cell type. We conclude that these characteristic histologic features are good predictors of EGFR mutations, and patients with these features might be good candidates for and could benefit from therapy with EGFR tyrosine kinase inhibitors.

Update in neoplastic lung diseases and mesothelioma

CONTEXT

Lung cancer is a common disease frequently seen by the surgical pathologist. Although secondary to improvements in screening and radiologic techniques and aggressive resection of small pulmonary nodules, the diagnosis of preneoplastic lesions is increasing in frequency and importance. Consequently, a greater understanding of their role in the development of lung carcinoma is needed for optimal patient care. Two lesions often encountered as small pulmonary nodules are bronchioloalveolar carcinoma and adenocarcinoma, which can be challenging to distinguish. Recently, updates to the TNM classification of non-small cell lung carcinoma have been reported that directly impact prognosis and treatment algorithms. Identification of new molecular targets in pleural mesothelioma and in preneoplastic lesions may lead to improved therapeutic strategies.

OBJECTIVE

To present recent advances in our understanding of neoplastic lung diseases and mesothelioma and to describe how these advances relate to the current practice of pulmonary pathology.

DATA SOURCES

Published literature from PubMed (National Library of Medicine) and primary material from the authors' institution.

CONCLUSIONS

It is important for the surgical pathologist to understand current diagnostic classifications of non-small cell lung cancer and to be aware of the range of preneoplastic lesions, as well as the features useful for distinguishing bronchioloalveolar carcinoma from adenocarcinoma in small pulmonary nodules. Although pleural mesothelioma has distinct features, it can also overlap histologically with adenocarcinoma, and immunohistochemistry can greatly aid in accurate diagnosis. New therapies targeting molecular markers in both non-small cell lung cancer and mesothelioma rely on accurate histopathologic diagnosis of these entities.

Cytologic diagnosis of pulmonary adenocarcinoma with micropapillary pattern: does it correlate with the histologic findings?

Micropapillary adenocarcinoma is associated with poor-prognosis in several organs including the lung. The presence of small tight balls of neoplastic cells devoid of fibrovascular core in cytological preparations (micropapillary tufts) has been described as characteristic of micropapillary adenocarcinoma. In the lung, however, this criterion has not been validated. The cytological material of 46 cases of histologically proven pulmonary adenocarcinoma with a micropapillary component was compared to 33 cases with no micropapillary component to determine the specificity of micropapillary tufts for the histologic diagnosis of micropapillary adenocarcinoma. Other histologic patterns of invasive pulmonary adenocarcinomas (acinar, papillary, and solid) were also compared with patterns of neoplastic cell aggregates in cytological preparations. There were no significant differences in the distribution of micropapillary clusters between the two groups. The positive predictive value for the cytologic diagnosis of a micropapillary component in lung adenocarcinomas was of 64%. Similar findings were observed for other invasive patterns. Therefore, the detection of micropapillary tufts in cytology is not specific for the diagnosis of a pulmonary micropapillary adenocarcinoma in the lung.

Micropapillary lung adenocarcinoma: EGFR, K-ras, and BRAF mutational profile

Micropapillary lung adenocarcinoma (MPA) has been reported as an aggressive variant of adenocarcinoma, frequently manifesting at high stage with a poor prognosis. We analyzed the clinical and molecular profile of 15 primary MPAs for K-ras, EGFR, and BRAF mutations and performed fluorescence in situ hybridization for EGFR amplification. In our study, 11 (73%) of 15 MPAs harbored mutually exclusive mutations: 5 (33%) K-ras, 3 (20%) EGFR, and 3 (20%) BRAF. Mutations in all 3 genes occurred in patients with a smoking history and tumors with mucinous differentiation and secondary lepidic, acinar, and solid growth, suggesting that in a Western population, cytomorphologic correlation with genetic mutations is more unpredictable than in Japanese cohorts. We conclude that K-ras, EGFR, and BRAF mutations are disproportionately seen in adenocarcinomas of lung with a dominant micropapillary growth pattern compared with conventional adenocarcinoma in our institutional experience.

Rapid progression of submucosal invasive micropapillary carcinoma of the colon in progressive systemic sclerosis: report of a case

A 71-year-old woman presented with hematochezia and narrowing of the stool. She suffered from progressive systemic sclerosis for 12 years and underwent home oxygen therapy due to pulmonary fibrosis and moderate pulmonary hypertension. Colonoscopy revealed a pedunculated, cauliflower-like polyp with a depressed surface in the sigmoid colon. The polyp was regarded as early colon cancer with possible submucosal invasion, and subsequent computed tomographic (CT) scans showed no evidence of lymph node involvement or distant metastases. Because of perioperative risks due to moderate pulmonary hypertension, she underwent an endoscopic resection of the early colon cancer. Pathological examination of the resected specimen of 20 mm diameter revealed the peculiar morphology of an adenocarcinoma with moderate lymphatic invasion. Immunohistochemical analysis for epithelial membrane antigen showed the specific 'inside-out growth pattern' indicative of invasive micropapillary carcinoma (IMPC). Taking the perioperative risks into consideration, she opted to undergo close follow-ups without an additional sigmoidectomy. At 6 months after the resection, the follow-up colonoscopy revealed a local recurrence of the colon cancer, and subsequent CT scans revealed multiple distant metastases including the lung, liver, lymph nodes and spleen. This is a rare case of a pure, submucosal IMPC of the colon. Furthermore, pure IMPC of the colon may represent a reliable predictor of lymphogenous and/or hematogenous metastases. Therefore, one should recommend an additional colectomy after endoscopic mucosal resection treatment when pathological findings confirmed IMPC of the colon and should continue a close follow-up for IMPC patients even when curative resections were performed at an early stage.

Small cluster invasion: a possible link between micropapillary pattern and lymph node metastasis in pT1 lung adenocarcinomas

Lung adenocarcinomas with micropapillary pattern (MPP) are associated with frequent nodal metastasis. However, little is known about the mechanisms that underlie MPP-associated nodal metastasis. In this study, we investigated how small micropapillary clusters of carcinoma cells present in tumoral alveolar spaces lead to increased lymph node metastasis. We analyzed 146 cases of pT1 lung adenocarcinomas with reference to the presence of MPP, small cluster invasion (SCI), and lymphatic involvement. SCI was defined as markedly resolved acinar-papillary tumor structures with single or small clusters of carcinoma cells invading stroma within fibrotic foci. The MPP-positive group (88/146 cases) was associated with significantly more frequent nodal metastasis and significantly worse survival. Moreover, SCI was significantly more frequent in the MPP-positive group (71/88 cases) than MPP-negative group (10/58 cases) and was significantly associated with lymphatic involvement (p < 0.0001) and nodal metastasis (p = 0.0073). The SCI-positive group showed significantly worse survival (5-year survival, 70%) than the SCI-negative group (91%, p = 0.0017). Carcinoma cells undergoing SCI demonstrated the same characteristic MUC-1 expression on the outer surface of cell clusters as those undergoing MPP. Thus, SCI could link MPP to nodal metastasis; carcinoma cells with MPP tend to undergo SCI in scars and invade lymphatics in pT1 lung adenocarcinomas.

Solitary and multiple resected adenocarcinomas after CT screening for lung cancer: histopathologic features and their prognostic implications

PURPOSE

To study the histopathologic features of CT screen-detected Stage IA adenocarcinomas to determine whether survival differed by the proportion of bronchioloalveolar component (BAC) or by the presence of multiple lesions in node-negative patients.

METHODS

Five pathologists with expertise in pulmonary pathology examined 279 resected cases of adenocarcinomas, 30 mm or less in length diagnosed by CT screening for lung cancer. The panel determined the consensus diagnosis for each case, identified additional cancers, and classified each case as solitary or non-solitary. The presence and proportion of BAC was also documented.

RESULTS

Of the cases of adenocarcinoma, 20 (7%) were BAC subtype, 246 (88%) mixed subtype and 13 (5%) adenocarcinoma-OTHER. BAC cases manifested as non-solid and part solid nodules, mixed as solid and part-solid, and other as solid only. Kaplan-Meier 10-year survival rates were 100% for BAC and adeno-MIXED with 90-99% BAC cases, 95% for mixed with 1-90% BAC, 90% for those without a BAC component, and 75% for other cases. Fifty (18%) cases were non-solitary carcinomas and 44 of these were node negative; the non-solitary node-negative cases had the same excellent prognosis as solitary node-negative cases.

CONCLUSIONS

The proportion of BAC component was a positive prognostic factor and correlated with CT consistency. Contrary to staging predictions, cases of non-solitary node-negative adenocarcinoma had the same excellent prognosis as solitary node-negative cases, suggesting that most of the small, node-negative multiple carcinomas probably represent multiple primaries rather than intrapulmonary metastasis.

Histopathological features and prognostic significance of the micropapillary pattern in lung adenocarcinoma

The micropapillary pattern is characterized by small papillary tufts with no fibrovascular core lying in spaces and has been reported as an aggressive variant of carcinoma in several organs. We investigated the histopathobiological properties of the micropapillary pattern with immunohistochemistry, serial sections, and electron microscopy in lung adenocarcinoma. We further analyzed its clinicopathological character and prognosis. The subjects included 383 adenocarcinoma cases, of which 184 (48%) were micropapillary pattern-positive and 199 (52%) were micropapillary pattern-negative. On histology, micropapillary tufts seemed to float in the alveolar space or spaces encased by connective tissues, whereas serial sections revealed that most tufts had continuity with other tufts and even with the main tumor. Positive staining for the adhesion molecules E-cadherin and beta-catenin suggested the preservation of tight adhesion, and electron microscopy showed the existence of intercellular junctions. Negative staining for laminin and loss of basement membrane as determined by electron microscopy suggest a loss of cell-matrix contact. Positive staining for Ki-67 indicates that cells constituting micropapillary tufts retained their proliferation potency. There were no CD34-positive cells in micropapillary tufts, and the loss of the vascular core was confirmed. In micropapillary pattern-positive cases, lymphatic invasion was identified significantly more frequently than in micropapillary pattern-negative cases (P<0.001), even at stageIA (without lymph node metastasis, N=197) (P<0.001). The 5-year and 10-year overall survival rates of the micropapillary pattern-positive stageIA group were 77.6 and 67.6%, respectively, which were significantly less than those of the micropapillary pattern-negative stageIA group (98.1 and 98.1%) (P=0.001). In conclusion, cells constituting the micropapillary pattern are likely to have acquired anchorage-independent growth and a potential for high malignancy.

Lung adenocarcinoma: modification of the 2004 WHO mixed subtype to include the major histologic subtype suggests correlations between papillary and micropapillary adenocarcinoma subtypes, EGFR mutations and gene expression analysis

The histologic heterogeneity of lung adenocarcinoma creates a variety of complex challenges to pathologists in analyzing the various subtypes. Current classification schemas do not take into account the major subtype. We analyzed 100 cases for clinical, pathologic, and molecular features using a modification of the 2004 World Health Organization (WHO) classification to record the major component in the mixed subtype tumors. The tumors were analyzed for KRAS mutation and epidermal growth factor receptor (EGFR) by mutation, chromogenic in situ hybridization, and immunohistochemistry for EGFR and phosphorylated EGFR. Gene expression analysis was performed using HG-U133A Affymetrix oligonucleotide microarrays revealing 3 gene clusters. The most common major histologic subtype was papillary (37%) followed by acinar (30%), solid (25%) and bronchioloalveolar (7%) carcinoma (BAC), although no pure BACs were seen. Sixteen tumors harbored EGFR mutations and 14 KRAS mutations. Papillary adenocarcinoma strongly correlated with EGFR mutation (P<0.001) and gene profile Cluster 1 (P=0.006) with weaker correlations with low grade (P=0.038) and favorable behavior in Stage 1 patients (P=0.047). Micropapillary subtype correlated strongly with EGFR mutation (P<0.001) and weakly with Cluster 1 (P=0.030). Solid adenocarcinoma strongly correlated with gene profile Cluster 3 (P=0.001) and worse survival (P=0.001). BAC as a major component strongly correlated with gene Cluster 2 (P=0.001). Cluster 1 correlated strongly with less smoking (P<0.001), papillary histology (P<0.001), and EGFR mutations (P<0.001). Cluster 3 strongly correlated with heavier smoking (P<0.001), larger tumor size (P<0.001), solid subtype (P<0.001), and poor grade (P=0.004); weak correlations were found with KRAS mutation (P=0.025). No correlation was found with BAC and EGFR by mutation, chromogenic in situ hybridization or immunohistochemistry. Higher stage (P<0.001), grade (P<0.001), and solid subtype (P=0.001) correlated with shorter survival. Our data suggest that EGFR mutations are associated with papillary adenocarcinoma and gene profile Cluster 1. We discovered this only because we used a comprehensive approach examining in detail all histologic subtypes and we modified the 2004 WHO mixed subtype to include the major histologic subtype. As we do not know the major genetic pathways of 30% to 70% of lung adenocarcinomas, the comprehensive histologic subtyping we propose gives advantage for recognition of unanticipated histologic-genetic correlations that might not be detected using classification systems that focus primarily on specific aspects of adenocarcinomas such as BAC or EGFR mutations. Such an approach should be considered in future studies for validation in other datasets.

Correlation between morphology and EGFR mutations in lung adenocarcinomas Significance of the micropapillary pattern and the hobnail cell type

The presence of epidermal growth factor receptor (EGFR) tyrosine kinase (TK) mutations significantly correlates with tumor sensitivity to TK inhibitors, particularly in lung adenocarcinomas, the predominant histological subtype in Japan and the United States. To clarify links between EGFR mutations and pathological findings in Japanese lung cancer, detailed pathological features of adenocarcinomas were examined using the WHO criteria as well as our cell type classification (hobnail, columnar and polygonal). Medical records were reviewed for a total of 107 surgically resected tumors. Clinicopathological factors were examined and correlations with EGFR status were evaluated. EGFR mutations were found in 63 patients (59%) distributed through all four exons examined (through exons 18-21). EGFR mutations were significantly associated with female gender (P=0.003), non-smoker status (P=0.008) and hobnail cell morphology (P<0.00001). In addition, detailed pathological examination showed significant associations with bronchioloalveolar carcinoma (BAC) component and a micropapillary pattern (MPP) (P=0.012 and 0.043, respectively). We conclude that characteristic histological features, i.e. the hobnail cell morphology and the presence of BAC component and MPP are good predictors of EGFR mutations in lung adenocarcinoma.

Micropapillary lung adenocarcinoma: a distinctive histologic subtype with prognostic significance. Case series

The aims of the present work were to evaluate the prognostic significance of the micropapillary pattern of lung adenocarcinoma and determine whether there are differences in the behavior of this type of tumor according to its immunohistochemical profile. A series of 191 consecutively resected pulmonary adenocarcinomas were divided into those with (n = 62) and those without (n = 129) micropapillary components. The disease was stage I in 38 and 54 patients, respectively. The 5-year survival rates of patients with and without micropapillary components were 54% and 77%, respectively (log rank P = .03). In multivariate survival analysis, the micropapillary component proved to be an independent prognostic factor (hazard ratio, 3.2). Five autopsy cases were used to investigate the immunohistochemical profile. The percentages of cases positive for various markers were 56.7 for p53, 94 for Ki67, 85.1 for c-myc, 2.9 for Bcl-2, 35.8 for epidermal growth factor receptor, 43.3 for cyclin D1, and 46.3 for Bax. The prognostic value was evaluated according to the expression of the different markers in micropapillary carcinomas in stage I. In univariate analysis, only cyclin D1 expression and Bax expression were associated with significantly worse survival (log rank P = .03 and P = .02, respectively). We conclude that it is important to recognize the micropapillary growth pattern in lung adenocarcinoma. Moreover, cyclin D1 and Bax seem to be markers of a poor prognosis.

A micropapillary pattern is predictive of a poor prognosis in lung adenocarcinoma, and reduced surfactant apoprotein A expression in the micropapillary pattern is an excellent indicator of a poor prognosis

A micropapillary pattern is defined as papillary tufts without a fibrovascular core and is known to be a factor that indicates a poor prognosis in numerous cancers. However, their role in lung adenocarcinoma has not been investigated widely. In 185 cases of small-size lung adenocarcinoma (< or =3 cm), cases with a micropapillary pattern ratio of more than 1% (analyzed by NIH image) were defined as micropapillary pattern positive. Correlations between the micropapillary pattern and clinicopathological factors were investigated and immunohistochemical expression of mucin and various antigens was examined in regions with and without micropapillary patterns. Micropapillary pattern-positive tumors (micropapillary pattern ratio > or =1%) were observed in 11.4% of cases (21/185) and the micropapillary pattern ratio correlated with TNM stage (P=0.0002), lymphatic invasion (P=0.0002) and lymph node metastasis (P=0.03). Disease-free interval (P<0.0002) and survival (P=0.027) were significantly shorter for micropapillary pattern-positive patients, and micropapillary pattern-positive stage IA cases also had a significantly shorter disease-free interval (P<0.0001). MUC1 was expressed strongly across the surface of the micropapillary structure, whereas MUC4 tended to show lower expression in the micropapillary pattern. It was noteworthy that the disease-free interval in patients with high surfactant apoprotein A expression was significantly better than in patients with low surfactant apoprotein A expression (P=0.03), and no recurrence or death occurred in patients with high surfactant apoprotein A expression. Our results show that the micropapillary pattern ratio correlates with lymphatic invasion and lymph node metastasis, and that a high micropapillary pattern ratio leads to a poor prognosis. High MUC1 expression on the surface is an important characteristic of a micropapillary pattern, and reduced surfactant apoprotein A expression in the micropapillary pattern may be an excellent indicator for poor prognosis in small-size lung adenocarcinoma.

[Therapeutic management of extensive bronchiolo-alveolar adenocarcinoma: chemotherapy or inhibitors of epidermal growth factor receptor tyrosine kinase?]

Although the 1999 WHO classification, revised in 2004 excludes stage IIIB-IV tumors from the definition of bronchioloalveolar carcinoma (BAC) because they are unresectable, the first international workshop (November 2004, New York) devoted to this tumor emphasized the continuum between the BAC as defined by the WHO and adenocarcinomas with a BAC-like component which presents similar epidemiological, biological, clinical, radiological, prognostic and therapeutic features. These observations led to the suggestion to no include stage IIIB-IV ADC-BAC in studies designed for other non-small-cell lung cancers. The purpose of this review was to analyze the results of prospective studies currently available concerning the treatment of stage IIIB-IV ADC-BAC. No evidence is available with combination regimens using platine. Monotherapy with paclitaxel appears to have efficacy similar to inhibitors of epidermal growth factor receptor tyrosine kinase (gefitinib and erlotinib) (TKI-EGFR). The tolerance profile is in favor of using TKI-EGFR. It would appear that tumors responding to paclitaxel and to TKI-EGFR correspond to different diseases. These observations point out the importance of further studies examining the proper strategy and to search for new compounds for the treatment of extensive ADC-BAC.

Micropapillary pattern and grade of stromal invasion in pT1 adenocarcinoma of the lung: usefulness as prognostic factors

Recently, the stromal invasion grading system was proposed for small adenocarcinomas of < or =2.0 cm. The system is based on the presence or absence of a fibrotic focus, and the extent of invasion into the fibrotic focus. Although stromal invasion grading system closely correlated with the prognosis, stromal invasion grade 3, representing stromal invasion into the center of a fibrotic focus, was the largest group of tumors and showed variable prognosis. In this study, we investigated whether stromal invasion grading system could be applied to and validated in pT1 adenocarcinomas as the TNM classification is the most universally used system. Furthermore, we investigated whether stromal invasion grade 3 cases could be subclassified according to the presence and absence of micropapillary pattern. The study included 120 cases of pT1 lung adenocarcinomas, of which 81 (68%) cases were stromal invasion grade 3. Micropapillary pattern was positive in 80% of grade 3 cases. For stromal invasion grade 3 cases, the 5-year survival rate of patients with micropapillary pattern-positive carcinomas was 63%, which was significantly worse than 94% of those with micropapillary pattern-negative carcinomas (P=0.0196). The latter was very close to that for patients with stromal invasion grade 0-2 (95%). Moreover, small cluster invasion was observed at sites of stromal invasion significantly more often in micropapillary pattern-positive cases than negative cases. Thus, the stromal invasion grading system is reproducible and correlates with prognosis even in pT1 lung adenocarcinomas. Moreover, among patients with stromal invasion grade 3 carcinomas, favorable prognosis is noted in micropapillary pattern-negative cases. The micropapillary pattern subclassification provides an advantage to the stromal invasion grading system and reconfirms the importance of micropapillary pattern as a prognostic marker. Our study is the first to point to the possible association of micropapillary pattern-positive carcinomas and small cluster invasion.

Histologic features are important prognostic indicators in early stages lung adenocarcinomas

This study attempts to evaluate the clinicopathologic features of mixed subtype adenocarcinomas and the prognostic implications of histopathology classifications. Surgical specimens from 141 patients with clinical stage I or II lung adenocarcinoma during the period 1992-2004 were included. These cases were classified into four groups defined by the extent of the bronchioloalveolar carcinoma component: group I: pure bronchioloalveolar carcinoma; group II: mixed subtype with predominant bronchioloalveolar carcinoma component and < or = 5 mm invasive component; group III: mixed subtype with bronchioloalveolar carcinoma component and > 5 mm invasive component; group IV: invasive carcinoma with no bronchioloalveolar carcinoma component. Descriptive statistics were used to examine the groups with respect to age, tumor size, lymph node metastasis, and Ki-67 and p53 expression levels. Death rate for the groups was obtained by patient's charts and from the National Death Index database. The population was similar in age, tumor size and lymph node metastasis. Immunohistochemical results showed that the mean Ki-67 labeling and the amount of p53 overexpression had the same trend of increasing mean values or positive results from groups I to IV. The reported proportion of deaths ranged from 0% for groups I and II, 20% in patients with predominant invasive component with bronchioloalveolar carcinoma (group III), and 18% in patients with invasive carcinomas and no bronchioloalveolar carcinoma component (group IV). The difference between the proportion of patients with reported deaths in the time period of this study in the combined greater than 5 mm+pure invasive groups (groups III, IV), and the < 5 mm + noninvasive groups (groups I, II) is statistically significant. These results suggest that histological features may be useful in defining categories of lung adenocarcinomas with differing survival and prognostic features. These results are helpful in defining a subcategory of 'minimally invasive adenocarcinoma', which has features similar to bronchioloalveolar carcinoma.

Lung adenocarcinoma with a micropapillary pattern: a clinicopathological study of 25 cases

Lung adenocarcinoma with a micropapillary pattern has recently been described, but its biological behavior is as yet uncertain. In this article we present a clinicopathological study of lung adenocarcinoma with micropapillary morphology. We selected 25 patients with lung adenocarcinoma with micropapillary morphology from the 2001-2004 pathology files (age range 54 to 81 years; mean 64.5 years). Micropapillary carcinoma is predominantly located at the periphery of the tumor nodule or mass and occurs irrespective of the subtype of the adenocarcinoma. A micropapillary component was seen against a mucinous background in three cases and microcalcifications resembling psammoma bodies were seen in one case. Four cases showed intensive invasive growth such as micropapillary adenocarcinoma of the breast and 21 showed alveolar type morphology with piling-up of the neoplastic cells with or without stromal invasion. Seven of twenty-three (30.4%) showed lymph node metastases at time of operation. Twelve of twenty-five (48%) showed pleural invasion. Regarding clinical outcome, 14 patients were alive without disease, 5 were alive with disease, and 5 died of the lung adenocarcinoma. No significant relationship was found between the extent of the micropapillary component and prognosis. However, the carcinoma seen in the five patients who died showed breast type histology with intensive invasive growth in three cases and alveolar type histology with intensive stromal invasion in two. Lung micropapillary carcinoma of breast type may behave more aggressively than the alveolar type.