Pulmonary Adenocarcinomas With Enteric Differentiation

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.

Co-activation of epidermal growth factor receptor and c-MET defines a distinct subset of lung adenocarcinomas

Epidermal growth factor receptor (EGFR) and MET are molecular targets for lung cancer treatment. The relationships between expression, activation, and gene abnormalities of these two targets are currently unclear. Here, we demonstrate that a panel of 40 lung cancer cell lines could be classified into two groups. Group I was characterized by (1) high phosphorylations of MET and EGFR, (2) frequent mutation or amplification of EGFR, MET, and human epidermal growth factor receptor-2 (HER2), (3) high expressions of bronchial epithelial markers (thyroid transcription factor-1 (TTF-1), MUC1, and Cytokeratin 7 (CK7)); and (4) high expressions of MET, human epidermal growth factor receptor-3, E-cadherin, cyclooxygenase-2, and laminin gamma2. In contrast, Group II exhibited little or no phosphorylation of MET and EGFR; no mutation or amplification of EGFR, MET, and HER2; were triple-negative for TTF-1, MUC1, and CK7; and showed high expressions of vimentin, fibroblast growth factor receptor-1, and transcription factor 8. Importantly, Group I was more sensitive to gefitinib and more resistant to cisplatin and paclitaxel than Group II. The clinical relevance was confirmed in publicly available data on 442 primary lung adenocarcinoma patients; survival benefits by postoperative chemotherapy were seen in only patients with tumors corresponding to Group II. Overall, co-activation of EGFR and MET defines a distinct subgroup of lung carcinoma with characteristic genetic abnormalities, gene expression pattern, and response to chemotherapeutic reagents.

Primary pulmonary adenocarcinoma with enteric differentiation resembling metastatic colorectal carcinoma: a report of the second case negative for cytokeratin 7

We report the case of a 51-year-old woman with pulmonary adenocarcinoma with enteric differentiation (PAED) that is indistinguishable from metastatic colorectal carcinoma by immunohistochemistry as well as histology. A chest computed tomography scan revealed a 1cm nodule in the right upper lobe and a 3cm mass in the left lower lobe. Initial examination showed no evidence of any other tumor. She underwent partial resection of the right upper lobe and left lower lobectomy. Histopathological examination revealed that both tumors were composed of medium to large complex glands with central necrosis. The tumor cells were cuboidal to tall columnar with eosinophilc cytoplasm, oval nuclei, and brush-border. Immunohistochemical study yielded the following results: tumor cells were diffusely positive for cytokeratin (CK) 20 and CDX-2, and negative for CK7, thyroid transcription factor-1, and Napsin A. MUC2 was partially observed, while MUC5AC was not detected. These findings were strongly indicative of metastatic colorectal carcinoma. However, no primary colorectal cancer was detected in any clinical examination, including fluorine 18-labeled fluorodeoxyglucose-positron emission tomography scan and video capsule endoscopy, and she has not presented with any characteristic symptoms at any follow-up to date, approximately 4 years after operation. From all features, the final diagnosis was primary PAED, suggestive of multifocal primary lung cancer. So far, only 1 case of CK7-negative PAED has been reported. This is the second case of primary PAED resembling metastatic colorectal cancer morphologically and immunohistologically.

The role of histology in idiopathic pulmonary fibrosis: an update

The diagnosis of idiopathic pulmonary fibrosis (IPF) currently requires an integrated clinical-radiological-pathological approach in which the histology plays a different role from in the past. The first reason for this change is that non-invasive diagnostic procedures, particularly pulmonary function tests and high resolution computed tomography, have become increasingly competitive with biopsy in providing prognostic information. The other reason is a better appreciation of the limitations of histology: sampling error and interobserver variation. In this review we analyze the reasons for this change of perspective, provide an update on the practical role of histology in the diagnosis of IPF and discuss some of its complications.

Mixed Adenocarcinomas of the Lung: Place in New Proposals in Classification, Mandatory for Target Therapy

Context.—Lung cancer is one of the most frequent and lethal malignant neoplasms, but knowledge regarding the molecular basis of its pathogenesis is far from complete due to the striking diversity of different forms. The current lung cancer classification (World Health Organization 2004) can efficiently distinguish clinically relevant major subtypes (small cell and non–small cell carcinomas), but its results are partly inadequate when facing prognostic and therapeutic decisions for non–small cell carcinomas, especially for the group of tumors classified as adenocarcinoma. Lung adenocarcinoma comprises a heterogeneous group of tumors characterized by diverse morphologic features and molecular pathogenesis. The category of mixed adenocarcinomas includes most adenocarcinomas (approximately 80%) and, according to World Health Organization criteria, is defined by the occurrence of a mixed array of different patterns (acinar, papillary, bronchioloalveolar, solid with mucin). The histologic recognition of mixed adenocarcinoma is subjective and cannot consistently discriminate between responders and nonresponders to new targeted therapies (eg, tyrosine kinase inhibitors). Diagnostic problems are mainly related to the poor reproducibility of histologic criteria, especially when applied in small biopsies and cytology, and to the difficulty in assigning each form to a precisely defined entity, as needed by updated therapeutic approaches. In this evolving scenario, pathologists face new challenging diagnostic roles that include not only the precise morphologic definition of carcinoma subtypes but also their molecular characterization.

Objective.—To use a comprehensive critical analysis reconciling the overwhelming variety of biologic, morphologic, molecular, and clinical data to define new classification schemes for lung adenocarcinoma.

Data Sources.—Scientific literature and personal data were used.

Conclusions.—A new classification approach should redefine lung adenocarcinoma heterogeneity reconciling classic morphology, immunophenotypic and molecular features of neoplastic cells, and also relevant information provided by stem cell biology. This approach, which has been already successfully applied in World Health Organization classification of other tumors, could improve the recognition of new reproducible profiles for adenocarcinomas, more closely and reproducibly related to clinical features and response to specific therapies, limiting the use of “wastebasket” categories such as mixed adenocarcinoma.

Synchronous lung tumours in a patient with metachronous colorectal carcinoma and a germline MSH2 mutation

Mutations of DNA mismatch repair genes are characterised by microsatellite instability and are implicated in carcinogenesis. This mutation susceptible phenotype has been extensively studied in patients with hereditary non-polyposis colon carcinoma, but little is known of the contribution of such mutations in other tumour types, particularly non-small-cell lung carcinoma. This report describes the occurrence of two synchronous lung tumours, one mimicking a metastatic colon carcinoma, in a male patient with a history of metachronous colonic carcinoma. Immunohistochemistry supported a pulmonary origin for both lesions. Mismatch repair protein immunohistochemistry showed loss of MSH2 and MSH6 expression in both colonic tumours and in one lung tumour showing enteric differentiation. Subsequent mutational analysis demonstrated a deleterious germline mutation of the MSH2 mismatch repair gene. The significance of these findings and the practical diagnostic difficulties encountered in this case are discussed.

EML4-ALK lung cancers are characterized by rare other mutations, a TTF-1 cell lineage, an acinar histology, and young onset

A subset of lung cancers harbors a small inversion within chromosome 2p, giving rise to a transforming fusion gene, EML4-ALK (echinoderm microtubule-associated protein-like 4 gene and the anaplastic lymphoma kinase gene), which encodes an activated tyrosine kinase. We have earlier examined the presence of EML4-ALK by multiplex reverse transcription-polymerase chain reaction in 363 specimens of lung cancer, identifying 11 adenocarcinoma cases featuring the fusion gene. In this study, we clinicopathologically examined the characteristics of the EML4-ALK-positive cases, including the mutation status of EGFR, KRAS, and TP53, and whether they were of thyroid transcription factor-1 (TTF-1) cell lineage or not. Of 11 patients, 4 (36%) with EML4-ALK-positive lung adenocarcinomas who were below 50 years of age were affected by these diseases, as compared with 12 of 242 patients (5.0%) with EML4-ALK-negative lung adenocarcinomas (P=0.00038). EML4-ALK-positive lung adenocarcinomas were characterized by less-differentiated grade (P=0.0082) and acinar-predominant structure (P<0.0001) in histology. Furthermore, the presence of EML4-ALK appears to be mutually exclusive for EGFR and KRAS mutations (P=0.00018), whereas coexisting with TP53 mutations at a low frequency (1/11=9.1%), and correlating with non- or light smoking (P=0.040), in line with the TTF-1 immunoreactivity. Thus, EML4-ALK-positive tumors may form a distinct entity among lung adenocarcinomas, characterized by young onset, acinar histology, no or rare mutations in EGFR, KRAS, and TP53, and a TTF-1 cell lineage, all in agreement with the prevalence in non- or light smokers.

Pathologic evaluation of unknown primary cancer

The pathologic approach to metastases of unknown primary cancer (UPC) is stepwise and uses the clinical context, morphology, and, where necessary, immunohistochemistry (IHC). This review covers the initial approach to a UPC biopsy; the diagnosis of malignancy and broad tumor typing into carcinoma, melanoma, lymphoma, or sarcoma; and further subtyping of carcinoma into germ cell (broadly included), squamous, neuroendocrine, and solid organ including liver and renal, and adenocarcinomas. Finally, for adenocarcinoma, the prediction of primary tumor site, including lung, pancreas, stomach, colon, ovary, prostate, and breast, is discussed. For each tumor type, the morphologic features are presented alongside established useful IHC markers, with a description of their staining patterns and common diagnostic dilemmas. Optimal tissue handling and IHC interpretation, quality assurance, and limitations also are discussed. The target readership is oncologists, but other clinicians and trainee pathologists also may find the content of use.

Primary pulmonary adenocarcinoma with intestinal differentiation mimicking metastatic colorectal carcinoma: case report and review of literature

Pulmonary adenocarcinoma with intestinal differentiation is rare and typically expresses proteins common to lung primaries. We report a case in a 51-year-old woman with a solitary 3.3-cm mass in the left lower lobe. Additional clinical investigation, including positron emission tomography scan with fluorine 18-labeled fluorodeoxyglucose, colonoscopy, and capsule endoscopy of her small bowel, revealed no evidence of tumor elsewhere. She underwent left lower lobectomy with mediastinal lymphadenectomy. Histologic examination revealed tall columnar cells without goblet cell differentiation arranged in a cribriform and acinar pattern with extensive central necrosis. Metastatic carcinoma was present in multiple hilar lymph nodes. Mediastinal lymph nodes were negative. Immunohistochemical stains demonstrated diffuse positivity for cytokeratin (CK) 20 and CDX-2 in neoplastic cells with negative staining for CK7 and thyroid transcription factor-1. CK7 expression has been documented in all 14 cases previously reported. This is the first description of pulmonary adenocarcinoma with intestinal differentiation with histopathologic and immunophenotypic findings indistinguishable from metastatic colorectal adenocarcinoma.

Avoiding underdiagnosis, overdiagnosis, and misdiagnosis of lung carcinoma

CONTEXT

Given the magnitude of the therapeutic and prognostic implications, it is critical that pathologists diagnose lung cancer accurately. This can sometimes be a formidable challenge, as a number of benign entities mimic lung carcinoma and vice versa.

OBJECTIVE

To present strategies for recognizing benign entities likely to be confused with lung carcinoma, malignancies of the lung prone to misinterpretation as benign, and commonly misclassified pulmonary neoplasms.

DATA SOURCES

The medical literature and experience from consultative and surgical practice.

CONCLUSIONS

In addition to understanding the clinical context in which a lung biopsy is procured and the radiographic findings, appreciating the histologic distribution of disease and what, if any, pathologic features are present in the background can go a long way toward averting a misdiagnosis of lung cancer. Recognizing the limitations posed by small samples and communicating clearly to clinicians the level of diagnostic uncertainty are equally as important for establishing an accurate diagnosis of lung cancer.

Immunohistochemistry of pulmonary and pleural neoplasia

CONTEXT

The use of immunohistochemical stains has several applications in the evaluation of pulmonary and pleural neoplasms. The number of available immunohistochemical stains is continually expanding and, although these stains are an important diagnostic adjunct, their use is not without limitations and pitfalls.

OBJECTIVE

To review and summarize the primary immunohistochemical applications with regard to the most common pulmonary and pleural neoplasms and discuss newly developed markers and common pitfalls.

DATA SOURCES

Pertinent peer-reviewed literature emphasizing immunohistochemical applications in common lung and pleural tumors, unusual and problematic staining patterns in frequently encountered subtypes/histologic variants, and recently developed immunohistochemical stains of potential promise.

CONCLUSIONS

Immunohistochemical stains provide the greatest aid in establishing the site of origin of adenocarcinomas encountered in the lung and in separating epithelioid mesothelioma from adenocarcinoma. Certain subtypes of pulmonary adenocarcinomas may exhibit unusual staining patterns that may be potentially problematic. Immunohistochemistry has a more limited role in separating small cell carcinoma from non-small cell carcinoma, and extreme caution must be used in the situation of crushed biopsy specimens.

Application of immunohistochemistry to the diagnosis of primary and metastatic carcinoma to the lung

CONTEXT

Immunohistochemistry is a very valuable and often used tool in the differential diagnosis of lung carcinomas whether primary or secondary to the lung. The most useful application is in distinguishing primary lung tumors from metastatic tumors to the lung from common sites (colon, breast, prostate, pancreas, stomach, kidney, bladder, ovaries, and uterus). Immunohistochemistry also aids in the separation of small cell carcinoma from non-small cell carcinoma and carcinoids particularly in small biopsy specimens limited by artifact. Although there is no "lung-specific tumor marker," with the help of a relatively restricted marker, thyroid transcription factor 1, it is possible to separate a lung primary from a metastasis with a reasonable degree of certainty. Another lung-specific marker on the horizon is napsin A, which appears to complement thyroid transcription factor 1 in defining a lung primary.

OBJECTIVE

To present a practical review and to critique commonly used markers in the differential diagnosis of lung neoplasms and to list valuable immunohistochemical prognostic markers that the pathologist is called on to perform and interpret.

DATA SOURCES

A comprehensive PubMed data search and personal practical experience.

CONCLUSIONS

With a panel of immunohistochemical markers, it is possible to distinguish or narrow down most lung neoplasms and separate them into meaningful therapeutic categories. In the future as more proteomic and genomic data surface, immunohistochemical markers to newly discovered antigens may become a routine part of prognostication.

Intestinal type adenocarcinoma: a previously unrecognized histologic variant of ductal carcinoma of the pancreas

Adenocarcinomas with intestinal differentiation have been described in a wide variety of anatomical sites. To our knowledge, however, ductal adenocarcinomas with intestinal phenotype have not been described in the pancreas. We report here 11 ductal carcinomas of the pancreas that were morphologically similar to colonic adenocarcinomas. These pancreatic carcinomas of intestinal type represented 10% of 110 consecutively removed ductal carcinomas of the pancreas. All intestinal type carcinomas expressed cytokeratin 7, carcinoembryonic antigen, CDX2, and MUC2. The pattern of reactivity of cytokeratin 7 and carcinoembryonic antigen was diffuse, whereas that of mucin 2 staining and CDX2 nuclear labeling was focal and confined predominantly to goblet cells and less frequently to columnar cells. Six carcinomas contained collections of endocrine cells admixed with the columnar and goblet cells. Five carcinomas were associated with high-grade pancreatic intraepithelial neoplasia of intestinal type. Six patients were female and 5 were male. Their ages ranged from 52 to 76 years (mean age, 61 years). The clinical presentation did not differ from that of the conventional ductal carcinomas. All carcinomas originated in the head of the pancreas, and 5 had metastasized to the regional lymph nodes at the time of surgical resection. Only 1 patient survived 5 years. Three patients are disease free from 2.8 to 8.9 months after surgery. Six patients died as a direct result of the carcinomas, and 1 was lost to follow-up. More studies are needed to determine the biologic behavior of this distinctive histologic variant of ductal adenocarcinoma of the pancreas.

CDX-2 expression in pseudomyxoma peritonei: a clinicopathological study of 42 cases

AIMS

CDX-2 is a highly sensitive and specific marker of intestinal epithelial cells and their neoplastic counterparts. CDX-2 status in pseudomyxoma peritonei (PMP) has been barely reported. The aim of this study was to investigate the clinicopathological features of 42 cases of PMP with a special emphasis on CDX-2.

METHODS AND RESULTS

All patients were treated by cytoreduction. Immunohistochemistry was performed for CDX-2, MUC-2, MUC-5AC, cytokeratin (CK) 7 and CK20. Statistical correlation was evaluated for age, sex, completeness of cytoreduction and histological subtype with overall and progression-free survival (OS and PFS). PMP consisted of 32 cases of disseminated peritoneal adenomucinosis and 10 cases of peritoneal mucinous carcinomatosis. The appendix evaluated in 25 cases showed two mucinous adenocarcinomas and 21 low-grade appendiceal mucinous neoplasms. CDX-2 was diffusely positive in 40 cases, with the remaining two cases being focally positive. All cases demonstrated diffuse reactions to CK20 and MUC-2, and variable reactions to MUC-5AC, while CK7 was variably positive in 38 cases. Five-year OS was 97%. Histological type was significantly correlated with PFS (P=0.02).

CONCLUSIONS

CDX-2 is diffusely and strongly positive in PMP. This is a useful marker to confirm an appendiceal origin of PMP, particularly when used in conjunction with CK7, CK20, MUC-2 and MUC-5AC.

Role of TTF-1, CK20, and CK7 immunohistochemistry for diagnosis of primary and secondary lung adenocarcinoma

Thyroid transcription factor-1 (TTF-1), and cytokeratin 7 (CK7) and cytokeratin 20 (CK20) have recently been reported to be useful to distinguish between primary and metastatic lung adenocarcinoma. The aim of this study was to determine the usefulness of the staining patterns of pulmonary adenocarcinoma with antibodies to TTF-1, CK7, and CK20 in differentiating primary from metastatic pulmonary adenocarcinoma. Of the 66 lung adenocarcinoma specimens that were enrolled in our study, there were 40 primary lung adenocarcinomas, 12 metastatic adenocarcinomas from breast, 13 metastatic adenocarcinomas from colon, and 1 metastatic adenocarcinoma from stomach. The expression of TTF-1, CK7, and CK20 was assessed by immunohistochemistry. We found that 73% of primary lung adenocarcinomas expressed TTF-1, whereas all nonpulmonary adenocarcinomas lacked TTF-1 staining. CK7 expression was significantly more frequent in adenocarcinomas of pulmonary and breast origin than gastrointestinal (GI) origin (p < 0.001). In contrast, CK20 expression was significantly more prevalent in adenocarcinoma that originated in the GI tract than that of pulmonary or breast origin (p < 0.001). A combination of TTF-1+CK7+CK20- was highly significantly associated with primary adenocarcinoma of lung (vs GI tract, p < 0.001; vs breast, p < 0.001). A combination of TTF-1-CKCK20+ was highly significantly associated with adenocarcinoma of GI origin (vs lung, p < 0.001; vs breast, p < 0.001). Our study has confirmed that expression of CK7, CK20, and TTF-1 is a useful immunohistochemical marker for diagnosis of lung tumors and for differential diagnosis of primary pulmonary adenocarcinomas from extrapulmonary adenocarcinomas metastatic to the lung. Application of this panel of antibodies might be expected to increase the accuracy of diagnosis.

Airway mucus: From production to secretion

Mucus hypersecretion is a phenotype associated with multiple obstructive lung diseases. However, in spite of its nefarious reputation under pathologic conditions, there are significant benefits to having low levels of mucus present in the airways at baseline, such as the ability to trap and eliminate inhaled particles and to prevent desiccation of airway surfaces. Mucins are high-molecular-weight glycoproteins that are the chief components that render viscoelastic and gel-forming properties to mucus. Recent advances in animal models and in vitro systems have provided a wealth of information regarding the identification of the mucin genes that are expressed in the lungs, the signal transduction pathways that regulate the expression of these mucins, and the secretory pathways that mediate their release into the airways. In addition, the clinical and pathologic literature has corroborated many of the basic laboratory findings. As a result, mucin overproduction and hypersecretion are moving away from being markers of disease and toward being testable as functional components of lung disease processes.