Expression of Squamous Cell Carcinoma Markers and Adenocarcinoma Markers in Primary Pulmonary Neuroendocrine Carcinomas

A critical appraisal of the clinico-radiological, histopathological and immunohistochemical profile of CT-guided and bronchoscopy-guided biopsies in lung lesions

BACKGROUND

Lung biopsies are obtained by bronchoscopy or by percutaneous route under image guidance and usually have limited tissue material. It is quite challenging for a pathologist to make an accurate diagnosis of lung cancer using only a limited panel of immunohistochemical markers and mucin stains as well as spare as much tissue for molecular testing.Molecular testing for specific genetic mutations or biomarkers serves as an adjunct for more rational, targeted treatment regimens.

METHODS

All the consecutive image-guided lung biopsies (both computed tomography [CT] guided and bronchoscopy-guided) for a period of 3 years (2021-2024) were included in the study. The clinicopathological data was compiled from the hospital records, and histopathology and immunohistochemistry (IHC) were analysed critically for all lung carcinomas. Sensitivity, specificity, negative predictive value, positive predictive value and diagnostic accuracy were calculated for IHC markers.

RESULTS

There were 127 lung biopsies (117 bronchoscopic and 10 CT-guided biopsies) comprise of adenocarcinoma (30%), squamous cell carcinoma (25.2%), small-cell carcinoma (13.4%) and poorly differentiated carcinoma (6.3%). The concordance between clinico-radiological and pathological diagnosis was 85%. P40 (22/22 cases) and CK5/6 (10/10) were the most sensitive and specific markers for squamous cell carcinoma, while TTF-1 (35/36) and Napsin A (18/22) were the most sensitive IHC markers for adenocarcinoma. The most sensitive markers for small-cell carcinoma lung were synaptophysin (17/17), CD 56, NSE followed by chromogranin A (11/15).

CONCLUSION

Integrating conventional histopathology with IHC results in accurate diagnosis, thereby avoiding a broad diagnosis of non-small-cell lung carcinoma (NSCLC). Subclassification of NSCLC has significant treatment implications, especially for advanced-stage tumours for which chemotherapy or targeted therapy is being considered. The focus should be on the judicious use of IHC based on histological type because of the limited availability of tissues in bronchoscopic and CT-guided biopsy specimens.

Utility of Immunohistochemistry in the Diagnosis of Pleuropulmonary and Mediastinal Cancers: A Review and Update

CONTEXT.—

Immunohistochemistry has become a valuable ancillary tool for the accurate classification of pleuropulmonary and mediastinal neoplasms necessary for therapeutic decisions and predicting prognostic outcome. Diagnostic accuracy has significantly improved because of the continuous discoveries of tumor-associated biomarkers and the development of effective immunohistochemical panels.

OBJECTIVE.—

To increase the accuracy of diagnosis and classify pleuropulmonary neoplasms through immunohistochemistry.

DATA SOURCES.—

Literature review and the author's research data and personal practice experience.

CONCLUSIONS.—

This review article highlights that appropriately selecting immunohistochemical panels enables pathologists to effectively diagnose most primary pleuropulmonary neoplasms and differentiate primary lung tumors from a variety of metastatic tumors to the lung. Knowing the utilities and pitfalls of each tumor-associated biomarker is essential to avoid potential diagnostic errors.

Transformation or tumor heterogeneity: Mutations in EGFR, SOX2, TP53, and RB1 persist in the histological rapid conversion from lung adenocarcinoma to small-cell lung cancer

The transformation from non-small-cell lung cancer (NSCLC) to small-cell lung cancer (SCLC) is one of the mechanisms of epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) resistance. Previous studies exhibited that the median transformation time was 17.8 months for NSCLC to SCLC. Here we introduced a case of lung adenocarcinoma (LADC) with EGFR19 exon deletion mutation in which the pathological transformation emerged only 1 month after lung cancer surgery and receiving EGFR-TKI inhibitor. Eventually, the pathological examination confirmed the patient experienced a transformation from LADC to SCLC with EGFR, tumor protein p53 (TP53), RB transcriptional corepressor 1 (RB1), and SRY-box transcription factor 2 (SOX2) mutation. Although the transformation of LADC with EGFR-mutant into SCLC after targeted therapy was frequent, the pathological results of most patients were only biopsy specimens, which cannot rule out the existence of mixed pathological components of the primary tumor. In this case, the patient's postoperative pathology was sufficient to exclude the probability of mixed tumor components, confirming that the patient's pathological change was indeed transformation from LADC to SCLC. In addition, primary drug resistance in such a short time after surgery and osimertinib-targeted therapy has not been reported before. We detected the molecular state of this patient before and after SCLC transformation through targeted gene capture and high-throughput sequencing, and also found for the first time that the mutations of EGFR, TP53, RB1, and SOX2 continue to exist before and after transformation, but the mutation abundance is different. In our paper, the occurrence of small-cell transformation is affected largely by these gene mutations.

Updates in pathology and molecular diagnostics to inform the evolving landscape of thoracic surgery and oncology

The pathologic assessment of lung cancers provides essential guidance to the surgeon and oncologist who are considering the best treatment strategies for patients with both early and advanced-stage disease. The management of patients with lung cancer is predicated first and foremost on access to an accurate diagnosis, even when the sample size is limited, as is often the case with use of modern, minimally invasive sampling techniques. Once the diagnosis and disease stage are established, predictive biomarker testing may be essential, particularly for those patients with nonsmall cell lung carcinoma (NSCLC) being considered for immunotherapy or genomic biomarker-driven targeted therapy. This review will discuss the best practices for the diagnosis of NSCLC using morphology and immunohistochemistry, thus providing the surgeon with needed information to understand and critically evaluate pathology reports. Controversial and evolving topics including tumor spread through airspaces, evaluation of multiple tumors, and staging based on invasive tumor size will be addressed. Clinical genomic profiling in NSCLC is driven by published guidelines and reflects evidence based on clinical trials and regulatory approvals. In this fast-moving space, surgeons should be aware of the critical immunohistochemical and genomic biomarkers that drive systemic therapy decisions and anticipate when such testing will be required, both to ensure adequate sampling and to advise the pathologist when tumor material will be required for biomarker analysis. The basic approaches to and sample requirements for molecular biomarker testing will be addressed. As biomarker testing moves exclusively from advanced-stage patients into earlier stage disease, the surgeon should be aware of the relevant markers and work with the pathologist and oncologist to ensure that this information is available to facilitate timely access to therapies not just in the advanced setting, but in consideration of neoadjuvant and adjuvant care.

Small Cell Lung Cancer, Version 2.2022, NCCN Clinical Practice Guidelines in Oncology

The NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines) for Small Cell Lung Cancer (SCLC) provide recommended management for patients with SCLC, including diagnosis, primary treatment, surveillance for relapse, and subsequent treatment. This selection for the journal focuses on metastatic (known as extensive-stage) SCLC, which is more common than limited-stage SCLC. Systemic therapy alone can palliate symptoms and prolong survival in most patients with extensive-stage disease. Smoking cessation counseling and intervention should be strongly promoted in patients with SCLC and other high-grade neuroendocrine carcinomas. The "Summary of the Guidelines Updates" section in the SCLC algorithm outlines the most recent revisions for the 2022 update, which are described in greater detail in this revised Discussion text.

SATB2 Is Expressed in a Subset of Pulmonary and Thymic Neuroendocrine Tumors

OBJECTIVES

To evaluate SATB2 expression and prognostic implications in a large cohort of thoracic neuroendocrine tumors.

METHODS

Surgical pathology files (1995-2017) and an institutional thymic epithelial tumor database (2010-2020) were searched for resected neuroendocrine tumors. Cases were stained with SATB2 (clone EP281). Percent SATB2-positive tumor cells and expression intensity were scored.

RESULTS

In the lung, SATB2 was expressed in 5% or more of tumor cells in 29 (74.4%) of 39 small cell carcinomas and 9 (22.5%) of 40 atypical and 26 (40.6%) of 64 typical carcinoid tumors. SATB2 percent tumor cell expression and intensity were higher in small cell carcinomas than in carcinoid tumors (both P < .001, respectively). After adjusting for tumor subtype, SATB2 expression did not correlate with outcome. In the thymus, four (100%) of four atypical carcinoid tumors and one large cell neuroendocrine carcinoma but no small cell carcinoma (n = 2) expressed SATB2 in 5% or more of tumor cells.

CONCLUSIONS

SATB2 (clone EP281) is expressed in a large subset of pulmonary and thymic neuroendocrine tumors and therefore does not appear to be a useful marker to identify the origin of neuroendocrine tumors. Validation studies are needed, specifically including thymic neuroendocrine tumors, as the expression pattern might be different in those tumors.

Immunocytochemistry for diagnostic cytopathology-A practical guide

Cytological specimens, which are obtained by minimally invasive methods, are an excellent source of diagnostic material. Sometimes they are the only material available for diagnosis as well as for prognostic/predictive markers. When cytomorphology is not straightforward, ancillary tests may be required for a definitive diagnosis to guide clinical management. Immunocytochemistry (ICC) is the most common and practical ancillary tool used to reach a diagnosis when cytomorphology is equivocal, to differentiate entities with overlapping morphological features, and to determine the cell lineage and the site of origin of a metastatic neoplasm. Numerous immunomarkers are available, and some are expressed in multiple neoplasms. To rule out entities within a differential diagnosis, the use of more than one marker, sometimes panels, is necessary. ICC panels for diagnostic purposes should be customised based on the clinical context and cytomorphology, and the markers should be used judiciously to preserve material for additional tests for targeted therapies in the appropriate setting. This review offers a practical guide for the use of ICC for diagnostic cytopathology, covering the most commonly encountered non-hematolymphoid diagnostic scenarios in various body sites.

The Unsupervised Feature Selection Algorithms Based on Standard Deviation and Cosine Similarity for Genomic Data Analysis

To tackle the challenges in genomic data analysis caused by their tens of thousands of dimensions while having a small number of examples and unbalanced examples between classes, the technique of unsupervised feature selection based on standard deviation and cosine similarity is proposed in this paper. We refer to this idea as SCFS (Standard deviation and Cosine similarity based Feature Selection). It defines the discernibility and independence of a feature to value its distinguishable capability between classes and its redundancy to other features, respectively. A 2-dimensional space is constructed using discernibility as x-axis and independence as y-axis to represent all features where the upper right corner features have both comparatively high discernibility and independence. The importance of a feature is defined as the product of its discernibility and its independence (i.e., the area of the rectangular enclosed by the feature’s coordinate lines and axes). The upper right corner features are by far the most important, comprising the optimal feature subset. Based on different definitions of independence using cosine similarity, there are three feature selection algorithms derived from SCFS. These are SCEFS (Standard deviation and Exponent Cosine similarity based Feature Selection), SCRFS (Standard deviation and Reciprocal Cosine similarity based Feature Selection) and SCAFS (Standard deviation and Anti-Cosine similarity based Feature Selection), respectively. The KNN and SVM classifiers are built based on the optimal feature subsets detected by these feature selection algorithms, respectively. The experimental results on 18 genomic datasets of cancers demonstrate that the proposed unsupervised feature selection algorithms SCEFS, SCRFS and SCAFS can detect the stable biomarkers with strong classification capability. This shows that the idea proposed in this paper is powerful. The functional analysis of these biomarkers show that the occurrence of the cancer is closely related to the biomarker gene regulation level. This fact will benefit cancer pathology research, drug development, early diagnosis, treatment and prevention.

Co-expression of SOX2 and HR-HPV RISH predicts poor prognosis in small cell neuroendocrine carcinoma of the uterine cervix

BACKGROUND

Small cell neuroendocrine carcinoma of the uterine cervix (SCNEC) is a rare cancer involving the human papilloma virus (HPV), and has few available treatments. The present work aimed to assess the feasibility of SOX2 and HPV statuses as predictive indicators of SCNEC prognosis.

METHODS

The associations of SOX2 and/or high-risk (HR)-HPV RNA in situ hybridization (RISH) levels with clinicopathological characteristics and prognostic outcomes for 88 neuroendocrine carcinoma (NEC) cases were analyzed.

RESULTS

Among these patients with SCNEC, SOX2, P16INK4A and HR-HPV RISH expression and SOX2/HR-HPV RISH co-expression were detected in 68(77.3%), 76(86.4%), 73(83.0%), and 48(54.5%), respectively. SOX2-positive and HR-HPV RISH-positive SCNEC cases were associated with poorer overall survival (OS, P = 0.0170, P = 0.0451) and disease-free survival (DFS, P = 0.0334, P = 0.0309) compared with those expressing low SOX2 and negative HR-HPV RISH. Alternatively, univariate analysis revealed that SOX2 and HR-HPV RISH expression, either separately or in combination, predicted the poor prognosis of SCNEC patients. Multivariate analysis revealed that the co-expression of SOX2 with HR-HPV RISH may be an independent factor of OS [hazard ratio = 3.597; 95% confidence interval (CI): 1.085-11.928; P = 0.036] and DFS [hazard ratio = 2.880; 95% CI: 1.199-6.919; P = 0.018] prediction in SCNEC.

CONCLUSIONS

Overall, the results of the present study suggest that the co-expression of SOX2 with HR-HPV RISH in SCNEC may represent a specific subgroup exhibiting remarkably poorer prognostic outcomes compared with the expression of any one marker alone.

An algorithmic approach utilizing CK7, TTF1, beta-catenin, CDX2, and SSTR2A can help differentiate between gastrointestinal and pulmonary neuroendocrine carcinomas

Primary gastrointestinal neuroendocrine carcinoma (GI-NEC) cannot be distinguished morphologically from pulmonary neuroendocrine carcinoma (P-NEC). This can present a significant diagnostic challenge in cases where site of origin cannot be readily determined. To identify immunohistochemical (IHC) markers that can be used to reliably distinguish between GI-NECs and P-NECs, we constructed 3-mm tissue microarrays, one containing 13 GI-NECs and one containing 20 P-NECs. IHC was performed on both microarrays using 21 stains: AE1/AE3, CK7, CK20, synaptophysin, chromogranin, CD56, INSM1, SSTR2A, CDX2, SATB2, TTF1, Napsin A, PR, GATA3, PAX8, ISL1, beta-catenin, AFP, SMAD4, Rb, and p53. For GI-NEC, the most strongly expressed marker was synaptophysin (mean H-score 248), while AE1/AE3 was the most strongly expressed in P-NEC (mean H-score 230), which was stronger than in GI-NEC (p = 0.011). Other markers that were stronger overall in P-NEC than in GI-NEC included CK7 (p < 0.0001) and TTF1 (p < 0.0001). Markers that were stronger overall in GI-NEC than in P-NEC included SSTR2A (p = 0.0021), SATB2 (p = 0.018), CDX2 (p = 0.019), and beta-catenin (nuclear; p = 0.029). SMAD4, Rb, and p53 showed similar rates of abnormal protein expression. Based on these results, a stepwise algorithmic approach utilizing CK7, TTF1, beta-catenin, CDX2, and SSTR2A had a 91% overall accuracy in distinguishing these GI-NEC from P-NEC. This was tested on a second cohort of 10 metastatic GI-NEC and 10 metastatic P-NEC, with an accuracy in this cohort of 85% and an overall accuracy of 89% for the 53 cases tested. Our algorithm reasonably discriminates GI-NEC from P-NEC using currently available IHC stains.

Multiple faces of pulmonary large cell neuroendocrine carcinoma: update with a focus on practical approach to diagnosis

Pulmonary large cell neuroendocrine carcinoma (LCNEC) is a rare and aggressive malignancy that is strongly linked to smoking and notoriously difficult to diagnose and treat. Recent molecular data reveal that it represents a biologically heterogeneous group of tumors, characterized by morphologic and genomic diversity that straddles small cell and non-small cell lung carcinomas (NSCLCs), and in a minority of cases atypical carcinoids. This review provides an update on recent molecular and clinical developments in LCNEC with the main focus on practical approach to pathologic diagnosis using illustrative examples of the main differential diagnostic considerations.

Immunohistochemical analysis of SOX2 expression in small-cell neuroendocrine carcinoma of the endometrium

Small-cell neuroendocrine carcinoma (NEC) of the endometrium is an extremely rare and highly aggressive carcinoma. Sex-determining region Y-box 2 (SOX2) is a master transcription factor regulating the self-renewal, maintenance of stem cell properties and pluripotency of embryonic stem cells, and recent studies revealed that SOX2 plays important roles in cancer growth and progression in several types of carcinomas, including small-cell neuroendocrine carcinoma (NEC) of the lung and oesophagus. Few studies to date have analysed the association between SOX2 and endometrioid carcinoma, whereas the expression of SOX2 in small-cell NEC of the endometrium has not been investigated. The aim of the present study was to analyse the expression status of SOX2, p16 and paired-box gene (PAX) 8, a useful Müllerian marker, in endometrial small-cell NEC. A total of 4 patients with small-cell NEC of the endometrium were enrolled (median age, 70 years). Immunohistochemical studies revealed SOX2 expression in 3 patients and p16 expression in all patients. No patients exhibited positive immunoreactivity for PAX8. SOX2 expression has been reported to be associated with the pathogenesis of small-cell NEC of the oesophagus. Therefore, the results of the present study indicated that SOX2 expression plays an important role in the development of small-cell NEC of the endometrium and the oesophagus. Moreover, expression of p16 and loss of PAX8 do not indicate the origin of small-cell NEC of the endometrium.

A practical guide for ancillary studies in pulmonary cytologic specimens

Although most pulmonary cytologic specimens obtained by either exfoliation or fine needle aspirates can be reliably and accurately diagnosed based on pure morphologic criteria alone, a small proportion of cases require ancillary studies for either refining a diagnosis, for resolving a differential diagnosis or increasingly, for predictive purposes in primary lung carcinomas. This article aims to provide practical guidance on the use of common ancillary studies in pulmonary cytologic specimens. Cancer Cytopathol 2018;000:000-000. © 2018 American Cancer Society.

Histopathological Spectrum and Immunohistochemical Profile of Lung Carcinomas: A 9-Year Study from a Tertiary Hospital in North India

Background:

Lung cancer is the most common cancer worldwide and the leading cause of cancer-related death. Diagnostic bronchoscopic or percutaneous biopsies are usually small. However, judicious use of immunohistochemistry (IHC) helps in accurate subtyping, which forms the basis for molecular tests and treatment.

Aim:

The aim was to study the role of IHC in the diagnosis of various histological subtypes of lung cancer.

Methods:

This 9-year study from 2009 to 2017 included all cases diagnosed as lung carcinoma on tissue biopsies. IHC markers were selected based on histopathology, from a panel comprising CK7, CK20, CK5/6, p63, thyroid transcription factor 1 (TTF-1), napsin A, synaptophysin, chromogranin A, neuron-specific enolase, CD56, and CDX2. Metastatic cancers to the lung were excluded from the study.

Results:

There were 199 cases of lung carcinoma comprising squamous cell carcinoma (37.7% [n = 75]), adenocarcinoma (26.1% [n = 52]), small cell carcinoma (20.6% [n = 41]), non-small cell lung carcinoma-unclassified (10.1% [n = 20]), adenosquamous carcinoma (2.5% [n = 5]), and others (3% [n = 6]). IHC was done on 47.7% (95/199) of cases. Squamous cell carcinomas showed CK5/6 and p63 positivity in 13/13 (100%) and 12/13 (92.3%) cases, respectively. Adenocarcinomas were positive for napsin A in 12/13 (92.3%) and TTF-1 in 35/41 (85.4%) cases. Neuroendocrine markers were positive in all small cell carcinomas.

Conclusion:

Squamous cell carcinoma was the most common primary lung malignancy in the North Indian population, followed by adenocarcinoma and small cell carcinoma. IHC panel of TTF-1, napsin A, CK5/6, and p63 is very helpful to classify most non-small cell lung carcinomas.

Overexpression of CD 133 and BCL-2 in non-small cell lung cancer with neuroendocrine differentiation after transformation in ALK rearrangement-positive adenocarcinoma

Transformation to small cell lung cancer is one phenomenon of acquired resistance to anaplastic lymphoma kinase (ALK) tyrosine kinase inhibitors in ALK rearrangement-positive non-small cell lung cancer (NSCLC). Few case reports have focused on other types of histological transformation. We report a case of transformation of ALK rearrangement-positive adenocarcinoma to NSCLC with neuroendocrine differentiation during alectinib therapy. A 36-year-old woman presented with a tumor in the left lower lobe and bone metastases. She was diagnosed with ALK rearrangement-positive adenocarcinoma by histopathology of the primary tumor. Alectinib had been effective for 8 months before new lesions appeared. Histopathological re-examination of a recurrent tumor revealed poorly differentiated carcinoma with insulinoma-associated protein 1 (INSM1) expression, which remained ALK-positive. Expression of CD133, BCL-2, and SOX2 was positive in comparison to the initial tumor. Expression of SOX2 became more strongly positive than it was before treatment. The immunohistochemical findings of these markers associated with cancer stem-like cells and/or neuroendocrine differentiation suggest that cancer stem cells play a role in the mechanisms of histological transformation and acquired resistance of ALK rearrangement-positive cancer. To our knowledge, this is the first report to suggest an association between cancer stem-like cells and histological transformation in ALK rearrangement-positive lung cancer.

Mucin staining is of limited value in addition to basic immunohistochemical analyses in the diagnostics of non-small cell lung cancer

Accurate diagnosis of histological type is important for therapy selection in lung cancer. Immunohistochemical (IHC) and histochemical stains are often used to complement morphology for definite diagnosis and are incorporated in the WHO classification. Our main aim was to compare different mucin stains and assess their value in relation to common IHC analyses in lung cancer diagnostics. Using tissue microarrays from 657 surgically treated primary lung cancers, we evaluated the mucin stains periodic acid-Schiff with diastase (PASD), alcian blue-periodic acid-Schiff (ABPAS) and mucicarmine, and compared with the IHC markers p40, p63, cytokeratin 5, thyroid transcription factor 1 (TTF-1), napsin A and cytokeratin 7. Ten or more cytoplasmic mucin inclusions in a tissue microarray core were seen in 51%, 48% and 31% of the 416 adenocarcinomas and 3%, 4% and 0.5% of the 194 squamous cell carcinomas with PASD, ABPAS and mucicarmine, respectively. Diagnostic pitfalls, such as entrapped benign epithelium, apoptotic/necrotic cells and glycogen, partly differed for the mucin stains. TTF-1 and napsin A IHC stainings had similar specificity but better sensitivity for adenocarcinoma than the mucin stains, but addition of PASD or ABPAS identified more tumors as adenocarcinomas (n = 8 and n = 10, respectively) than napsin A (n = 1) in cases with solid growth that were negative for TTF-1 and p40. We conclude that PASD and ABPAS have similar diagnostic performance and that these markers are of value in poorly differentiated cases. However, morphology and TTF-1 and p40 IHC staining is sufficient for correct diagnosis in most non-small cell lung cancers.

Updates in Lung Cancer Cytopathology

Lung cancer diagnosis and ancillary testing are increasingly relying on cytology and small biopsy specimens obtained via minimally invasive means. Paired with traditional immunohistochemical characterization of tumors, biomarker testing and comprehensive genomic profiling are becoming essential steps in the workup of lung cancer to identify targetable alterations and guide optimal therapy selection. Recent advances in immune checkpoint inhibitor therapy have led to an increasingly complex and unresolved landscape for tumor PD-L1 testing. The prevalence and importance of lung cancer cytology specimens are growing, with more required by the cytopathologist in directing the care of patients with lung cancer.

Characteristics of surfactant proteins in tumorigenic and inflammatory lung lesions in rodents

Surfactant proteins (SPs) are essential for the proper structure and respiratory function of the lungs. There are four subtypes of SPs: SP-A, SP-B, SP-C, and SP-D. The expectorant drug ambroxol hydrochloride is clinically used to stimulate pulmonary surfactant and airway serous secretion. In addition, previous studies showed that ambroxol regulated SP production and attenuated pulmonary inflammation, with ambroxol hydrochloride being found to suppress quartz-induced lung inflammation via stimulation of pulmonary surfactant and airway serous secretion. In this study, we investigated the expression of SP-A, SP-B, SP-C, and SP-D in neoplastic and inflammatory lung lesions in rodents, as well as their possible application as potential markers for diagnostic purposes. SP-B and SP-C showed strong expression in lung hyperplasia and adenoma, whereas SP-A and SP-D were expressed in the mucus or exudates of inflammatory alveoli. Rodent tumorigenic hyperplasic tissues induced by various carcinogens were positive for napsin A, an aspartic proteinase involved in the maturation of SP-B; this indicated a focal increase in type II pneumocytes in the lungs. Therefore, high expression of napsin A in the alveolar walls may serve as a useful marker for prediction of the tumorigenic potential of lung hyperplasia in rodents.

Pulmonary large cell neuroendocrine carcinoma with adenocarcinoma-like features: napsin A expression and genomic alterations

Pulmonary large cell neuroendocrine carcinoma (LCNEC) is a highly aggressive malignancy, which was recently found to comprise three major genomic subsets: small cell carcinoma-like, non-small cell carcinoma (predominantly adenocarcinoma)-like, and carcinoid-like. To further characterize adenocarcinoma-like subset, here we analyzed the expression of exocrine marker napsin A, along with TTF-1, in a large series of LCNECs (n=112), and performed detailed clinicopathologic and genomic analysis of napsin A-positive cases. For comparison, we analyzed napsin A expression in other lung neuroendocrine neoplasms (177 carcinoids, 37 small cell carcinomas) and 60 lung adenocarcinomas. We found that napsin A was expressed in 15% of LCNEC (17/112), whereas all carcinoids and small cell carcinomas were consistently negative. Napsin A reactivity in LCNEC was focal in 12/17 cases, and weak or moderate in intensity in all cases, which was significantly lower in the extent and intensity than seen in adenocarcinomas (P<0.0001). The combination of TTF-1-diffuse/napsin A-negative or focal was typical of LCNEC but was rare in adenocarcinoma, and could thus serve as a helpful diagnostic clue. The diagnosis of napsin A-positive LCNECs was confirmed by classic morphology, diffuse labeling for at least one neuroendocrine marker, most consistently synaptophysin, and the lack of distinct adenocarcinoma component. Genomic analysis of 14 napsin A-positive LCNECs revealed the presence of mutations typical of lung adenocarcinoma (KRAS and/or STK11) in 11 cases. In conclusion, LCNECs are unique among lung neuroendocrine neoplasms in that some of these tumors exhibit low-level expression of exocrine marker napsin A, and harbor genomic alterations typical of adenocarcinoma. Despite the apparent close biological relationship, designation of adeno-like LCNEC as a separate entity from adenocarcinoma is supported by their distinctive morphology, typically diffuse expression of neuroendocrine marker(s) and aggressive behavior. Further studies are warranted to assess the clinical utility and optimal method of identifying adenocarcinoma-like and other subsets of LCNEC in routine practice.

SMARCA4-deficient thoracic sarcoma: a distinctive clinicopathological entity with undifferentiated rhabdoid morphology and aggressive behavior

A distinct subset of thoracic sarcomas with undifferentiated rhabdoid morphology and SMARCA4 inactivation has recently been described, and potential targeted therapy for SMARC-deficient tumors is emerging. We sought to validate the clinicopathological features of SMARCA4-deficient thoracic sarcomas. Clinicopathological information was gathered for 40 undifferentiated thoracic tumors with rhabdoid morphology (mediastinum (n=18), lung (n=14), pleura (n=8)). Thymic carcinomas (n=11) were used as a comparison group. Immunohistochemistry included BRG1 (SMARCA4), BRM (SMARCA2), INI-1 (SMARCB1), pan-cytokeratin, desmin, NUT, S-100 protein, TTF1, CD34, and SOX2. BRG1 loss was present in 12 of 40 rhabdoid thoracic tumors (30%): 7 of 18 in mediastinum (39%), 2 of 8 in pleura (25%), and 3 of 14 in lung (21%). All BRG1-deficient tumors tested for BRM (n=8) showed concomitant loss. All thymic carcinomas showed retained BRG1 and INI-1. Morphologically, tumors with BRG1 loss showed sheets of monotonous ovoid cells with indistinct cell borders, abundant eosinophilic cytoplasm, and prominent nucleoli. Scattered areas with rhabdoid morphology (ie, eccentric nuclei, dense eosinophilic cytoplasm, discohesion) were present in all the cases. SMARCA4/BRG1-deficient sarcomas showed rare cells positive for cytokeratin in 10 cases (83%). One showed rare TTF1-positive cells. All were negative for desmin, NUT, and S-100 protein. CD34 was positive in three of five (60%) BRG1-deficient tumors tested. SOX2 was positive in all four BRG1-deficient tumors tested, and negative in all seven tested cases with retained BRG1. SMARCA4/BRG1-deficient sarcomas occurred at median age of 59 years (range 44-76) with male predominance (9:3) and had worse 2-year survival compared with BRG1-retained tumors (12.5% vs 64.4%, P=0.02). SMARCA4-deficient thoracic sarcomas can be identified based on their distinctive high-grade rhabdoid morphology, and the diagnosis can be confirmed by immunohistochemistry. Identification of these tumors is clinically relevant due to their aggressive behavior, poor prognosis, and potential targeted therapy.

Validating the use of napsin A as a marker for identifying tumorigenic potential of lung bronchiolo-alveolar hyperplasia in rodents

There are two types of bronchiolo-alveolar hyperplasia (hyperplasia) in rodent lungs. The first is "inflammatory hyperplasia" that retains its ability to revert to normal epithelia upon removal of the stimulating insult. The second is "latent tumorigenic hyperplasia", which is irreversible and causes independent preneoplastic lesions that can progress to bronchiolo-alveolar adenocarcinoma. Previously, lung samples with hyperplastic lesions were obtained from rats exposed to N-bis (2-hydroxypropyl) nitrosamine (DHPN) and fine particles (e.g. quartz), and 19 specific markers were examined immunohistochemically to identify latent tumorigenic hyperplasia. In the cytoplasm of the cells that make up the alveolar wall, we found that napsin A was weakly expressed in the inflammatory hyperplastic lesions, and was strongly expressed in the latent tumorigenic hyperplastic lesions induced by DHPN. To validate the possibility that napsin A may serve as a tumorigenic hyperplastic marker, additional experiments were performed with rats and mice. Latent tumorigenic hyperplasia induced by various carcinogens were positive for napsin A, similar to hyperplasia induced by DHPN. Thus, high expression of napsin A in alveolar walls may serve as a useful marker for detecting the tumorigenic potential of lung hyperplasia in rodents.

Gene Expression Profiling of Large Cell Lung Cancer Links Transcriptional Phenotypes to the New Histological WHO 2015 Classification

INTRODUCTION

Large cell lung cancer (LCLC) and large cell neuroendocrine carcinoma (LCNEC) constitute a small proportion of NSCLC. The WHO 2015 classification guidelines changed the definition of the debated histological subtype LCLC to be based on immunomarkers for adenocarcinoma and squamous cancer. We sought to determine whether these new guidelines also translate into the transcriptional landscape of lung cancer, and LCLC specifically.

METHODS

Gene expression profiling was performed by using Illumina V4 HT12 microarrays (Illumina, San Diego, CA) on samples from 159 cases (comprising all histological subtypes, including 10 classified as LCLC WHO 2015 and 14 classified as LCNEC according to the WHO 2015 guidelines), with complimentary mutational and immunohistochemical data. Derived transcriptional phenotypes were validated in 199 independent tumors, including six WHO 2015 LCLCs and five LCNECs.

RESULTS

Unsupervised analysis of gene expression data identified a phenotype comprising 90% of WHO 2015 LCLC tumors, with characteristics of poorly differentiated proliferative cancer, a 90% tumor protein p53 gene (TP53) mutation rate, and lack of well-known NSCLC oncogene driver alterations. Validation in independent data confirmed aggregation of WHO 2015 LCLCs in the specific phenotype. For LCNEC tumors, the unsupervised gene expression analysis suggested two different transcriptional patterns corresponding to a proposed genetic division of LCNEC tumors into SCLC-like and NSCLC-like cancer on the basis of TP53 and retinoblastoma 1 gene (RB1) alteration patterns.

CONCLUSIONS

Refined classification of LCLC has implications for diagnosis, prognostics, and therapy decisions. Our molecular analyses support the WHO 2015 classification of LCLC and LCNEC tumors, which herein follow different tumorigenic paths and can accordingly be stratified into different transcriptional subgroups, thus linking diagnostic immunohistochemical staining-driven classification with the transcriptional landscape of lung cancer.

SOX2 and Rb1 in esophageal small-cell carcinoma: their possible involvement in pathogenesis

Clinicopathological features and pathogenesis of esophageal small-cell carcinoma remain unclear. We hypothesized common cellular origin and pathogenesis in small-cell carcinoma of esophagus and lung associated with SOX2 overexpression and loss of Rb1. Expression of squamous-basal markers (CK5/6 and p40), glandular markers (CK18 and CEA), SOX2, and Rb1 were evaluated in 15 esophageal small-cell carcinomas, 46 poorly differentiated squamous cell carcinomas, and 88 small-cell lung carcinoma, as well as 16 embryonic esophagus. Esophageal small-cell carcinoma expressed higher levels of glandular markers and lower levels of squamous-basal markers than poorly differentiated squamous cell carcinoma. No significant differences were observed in immunohistochemistry profiles between small-cell carcinoma of the esophagus and the lung. SOX2 expression was high in esophageal small-cell carcinoma (70%±33% of nuclei), small-cell lung carcinoma (70%±26%), and the embryonic esophagus (75%±4%), and it was significantly lower in poorly differentiated squamous cell carcinoma (29%±28%). Rb1 expression was significantly lower in esophageal small-cell carcinoma (0.3%±1%), small-cell lung carcinoma (2%±6%), and the embryonic esophagus (7%±5%), and it was significantly higher in poorly differentiated squamous cell carcinoma (51%±24%). The immunohistochemistry profiles of small-cell carcinoma of the esophagus and the lung are highly similar. The loss of Rb1 function is a key contributor to the pathogenesis of both neoplasms. In addition, SOX2 overexpression observed in esophageal and lung small-cell carcinoma as well as in the embryonic esophagus indicated that esophageal small-cell carcinoma may arise from embryonic-like stem cells in the esophageal epithelium. The two distinct differentiation patterns (neuroendocrine and glandular) of esophageal small-cell carcinoma further support the fact that SOX2 has a pivotal role in the differentiation of pluripotent stem cells into esophageal small-cell carcinoma cells.

Recent updates on grading and classification of neuroendocrine tumors

Neuroendocrine tumors (NETs) are originating from neuroendocrine cells in diffuse endocrine systems. NETs are diagnosed by characteristic histologic features and immunoprofiles. Recent 2010 WHO classification for gastroenteropancreatic NETs introduced grading system based on mitotic count and Ki-67 proliferation index. Gastroenteropancreatic NETs are classified as NET grade 1, NET grade 2, and neuroendocrine carcinoma (NET grade 3). However, the carcinoid is still used in classification of NETs of the lung and uterine cervix. Some issues with grading system such as methodologies for evaluation of Ki-67 index and subclassification of neuroendocrine carcinoma (NET grade 3) are arising. The importance of Ki-67 labeling index is emerging in differential diagnosis of lung carcinoids. In this review, we focus on recent grading and classification of NETs and related issues in various organs, including gastrointestinal tract, pancreas, lung, and female reproductive organs.

The impact of immunohistochemistry on the classification of lung tumors

INTRODUCTION

To highlight the role of immunohistochemistry to lung cancer classification on the basis of existing guidelines and future perspectives.

AREAS COVERED

Four orienting key-issues were structured according to an extensive review on the English literature: a) cancer subtyping; b) best biomarkers and rules to follow; c) negative and positive profiling; d) suggestions towards an evidence-based proposal for lung cancer subtyping. A sparing material approach based on a limited number of specific markers is highly desirable. It includes p40 for squamous cell carcinoma ('no p40, no squamous'), TTF1 for adenocarcinoma, synaptophysin for neuroendocrine tumors and vimentin for sarcomatoid carcinoma. A close relationship between genotype and phenotype also supports a diagnostic role for negative profiles. Expert commentary: Highly specific and sensitive IHC markers according to positive and negative diagnostic algorithms seem appropriate for individual patients' lung cancer subtyping.

Histopathologic and Cytogenetic Features of Pulmonary Adenoid Cystic Carcinoma

INTRODUCTION

A significant portion of adenoid cystic carcinoma (ACC) cases are characterized by a t(6;9)(q22-23;p23-24) translocation that originates a MYB-NFIB fusion oncogene. The MYB-NFIB fusion oncoprotein activates transcription of MYB-mediated pathways that impact cell cycle control, DNA repair, and apoptosis. This translocation seems highly specific for ACC. Moreover, therapies targeting MYB-activated pathways to treat ACC are being explored. Pulmonary ACC (PACC) has not been thoroughly studied for rearrangements of the MYB gene.

METHODS

Mayo Clinic Rochester surgical pathology archives (1972-2011) were searched for PACC. All cases were reviewed and classified according to the predominant histologic pattern (cribriform, solid, and tubular) by two surgical pathologists. Fluorescence in situ hybridization (FISH) was employed using a break-apart strategy to detect MYB rearrangement (at 6q23.3). Medical records were studied.

RESULTS

Forty cases of PACC were studied; tissue blocks were available for FISH analysis in 35 cases. Six cases failed to hybridize. In 12 of 29 cases (41%), the MYB gene region was disrupted, whereas 17 cases (59%) showed no evidence of rearrangement. FISH studies performed on other histologic subtypes of lung cancer (10 squamous cell carcinomas, 10 adenocarcinomas, and 10 small-cell carcinomas) failed to show MYB rearrangement. There was no significant difference in MYB rearrangement status with respect to predominant histologic pattern, clinical features, or clinical outcome.

CONCLUSIONS

A MYB rearrangement was identified in 41% of PACC and was 100% specific. FISH studies for MYB may be of diagnostic utility in PACC, particularly on small biopsy specimens. MYB rearrangement in PACC does not seem to be associated with clinical features or prognosis.

Chronic mesothelial reaction and toxicity of potassium octatitanate fibers in the pleural cavity in mice and F344 rats

Fiber‐shaped particles of potassium octatitanate (tradename TISMO; chemical formula K₂O·6TiO₂), which are morphologically similar to asbestos particles, were shown to induce severe proliferative reactions in the pleural mesothelium in a previous experiment carried out over 21 weeks. The present study aims to determine whether these fibers induce malignant mesotheliomas in rodents, and to examine chronic toxicity induced. Additionally, we investigated the specific differences observable between the biological responses to the direct infusion of the fibers alone into the pleural cavity and those induced by the co‐administration of the fibers with a known carcinogen. To detect the induction of malignant pleural mesotheliomas, two experiments were undertaken. In Experiment 1, four strains of mice, A/J, C3H, ICR, and C57BL, were examined for 52 weeks after experimental treatment with TISMO. In Experiment 2, the F344 rats were treated with TISMO alone, the lung carcinogen N‐bis (2‐hydroxypropyl) nitrosamine (DHPN) alone, both TISMO and DHPN, or left untreated and were then examined for 52 weeks. In this experiment, malignant lesion induction was expected in the co‐administration group. TISMO fibers were observed in the alveoli, indicating penetration through the visceral pleura in mice and rats. The histopathological detection of TISMO fibers in the liver and kidneys of mice and rats indicated migration of the fibers out of the pleural cavity. Atypical mesothelial cells with severe pleural proliferation were observed, but malignant mesotheliomas were not detected. Among the rats, there were no observed malignant alterations in the mesothelium induced by DHPN–TISMO co‐administration.

Expression of P40 and P63 in lung cancers using fine needle aspiration cases. Understanding clinical pitfalls and limitations

BACKGROUND

Fine-needle aspiration (FNA) biopsy of lung lesions is a highly accurate method for diagnosing and staging of lung cancers, particularly in patients with advanced cancer. Although, the majority of FNA cases of non-small cell lung carcinoma (NSCLC) can be subclassified by hematoxylin and eosin (H&E) sections, immunohistochemical (IHC) markers are usually necessary for difficult cases. Our previous study has shown that both P40 and P63 demonstrate differential sensitivity and specificity in the subclassification of squamous cell carcinoma (SqCC) using tumor tissue microarrays (TMA). In the present study, we further evaluated the utility of P40 and P63 and the potential pitfalls and limitations associated with the usefulness of these stains in FNA cases.

METHODS

By a computer search of pathology archives, 144 FNA biopsies with diagnoses of lung cancers and P40/P63 stains were identified, including 50 adenocarcinomas (ADCs), 56 SqCCs, 8 small cell lung carcinomas (SCLCs), and 12 cases of poorly differentiated carcinoma (PD CA). Ten benign FNA lung lesions and 8 other malignant neoplasms were also included as controls. Nuclear staining patterns of P40 and P63 were scored semi-quantitatively as 0 (negative), 1 (<10%, weak and focal), or 2 (>10%, strong and diffuse).

RESULTS

In lung SqCCs, P40 and P63 were positive in 77.3% and 89.5% cases, respectively. In ADCs, P40 was weakly and focally positive in 6.1% cases, and P63 was variably positive in 62.8% cases. In SCLCs, P40 and P63 were focally positive in 12.5% and 50% cases. In PD CAs, no P40 or P63 immunoreactivity was detected. In the group of other neoplasms (n=8) both P40 and P63 were positive in the case of metastatic non-seminomatous germ cell tumor (NSGCT) (n=1), and P63 was positive in the case of metastatic Merkel cell carcinoma (n=1). The sensitivity and specificity of P40 and P63 were 76.9%/93.3%, and 90.2%/50.7% in the lung SqCC.

CONCLUSIONS

P63 has a better sensitivity, and P40 has a better specificity for SqCC. A positive staining pattern with both markers was also found in certain non-SqCC cases. Recognizing limitations of these markers are particularly important in FNA cases.

Impact of non-small-cell lung cancer-not otherwise specified immunophenotyping on treatment outcome

INTRODUCTION

The vast majority of non-small-cell lung cancers (NSCLCs) presents as advanced disease, and histological diagnosis is widely based on small samples. The differential activity and toxicity profile of new cytotoxic and molecular-targeted therapies according to histotypes requires a precise subtyping of NSCLC. Immunohistochemistry (IHC) contributes to define the most probable histotype; however, the real impact of IHC characterization of NSCLC-not otherwise specified (NOS) in terms of outcome is not well established.

METHODS

A large series of 224 advanced "nonsquamous" NSCLC diagnosed on small biopsy or cytological samples and homogeneously treated was retrospectively selected, all having adequate follow-up data available. Reviewed diagnoses resulted into two groups: adenocarcinoma (ADC) and NSCLC-NOS. The latter was further characterized by IHC (TTF-1, Napsin-A, p40, and Desmocollin-3) -identify a possible, most probable differentiation lineage.

RESULTS

Sixty-seven percentage of cases were classified as ADC based on morphological examination only ("morphological ADC") and 33% as NSCLC-NOS. IHC profiling of NSCLC-NOS identified 43.2% of cases with an ADC immunophenotype ("NSCLC favor ADC"), 10.8% with a phenotype favoring squamous lineage, and 46% lacking differentiation features. Survival curves confirmed no difference in terms of outcome between the morphological ADC and the NSCLC favor ADC groups, while a significantly poorer outcome was found in the "null" group in terms of best response, progression-free survival or overall survival (OS).

CONCLUSION

Tumors with an IHC profile ADC-like had an OS comparable with that of morphological ADCs. These findings support the use of IHC to optimize lung cancer histological typing and therapy.

Utility of Immunohistochemistry in the Diagnosis of Pleuropulmonary and Mediastinal Cancers: A Review and Update

Context

Immunohistochemistry has become an indispensable ancillary tool for the accurate classification of pleuropulmonary and mediastinal neoplasms necessary for therapeutic decisions and predicting prognostic outcome in the era of personalized medicine. Diagnostic accuracy has significantly improved because of the continuous discoveries of tumor-associated biomarkers and the development of effective immunohistochemical panels.

Objective

To increase the accuracy of diagnosis and classify pleuropulmonary neoplasms through immunohistochemistry.

Data Sources

Literature review, authors' research data, and personal practice experience.

Conclusions

This review article has shown that appropriately selecting immunohistochemical panels enables pathologists to effectively diagnose most primary pleuropulmonary neoplasms and differentiate primary lung tumors from a variety of metastatic tumors to the lung. The discovery of new mutation-specific antibodies identifying a subset of specific gene-arranged lung tumors provides a promising alternative and cost-effective approach to molecular testing. Knowing the utilities and pitfalls of each tumor-associated biomarker is essential to avoiding potential diagnostic errors.

Immunohistochemical characteristics of surfactant proteins a, B, C and d in inflammatory and tumorigenic lung lesions of f344 rats

Surfactant proteins (SPs), originally known as human lung surfactants, are essential to respiratory structure and function. There are 4 subtypes, SP-A, SP-B, SP-C and SP-D, with SP-A and SP-D having immunological functions, and SP-B and SP-C having physicochemical properties that reduce the surface tension at biological interfaces. In this experiment, the expressions of SP-A, SP-B, SP-C and SP-D in lung neoplastic lesions induced by N-bis (2-hydroxypropyl) nitrosamine (DHPN) and inflammatory lesions due to quartz instillation were examined and compared immunohistochemically. Formalin fixed paraffin embedded (FFPE) lung samples featuring inflammation were obtained with a rat quartz instillation model, and neoplastic lesions, hyperplasias and adenomas, were obtained with the rat DHPN-induced lung carcinogenesis model. In the rat quartz instillation model, male 10-week old F344 rats were exposed by intratracheal instillation (IT) to quartz at a dose of 2 mg/rat suspended in saline (0.2 ml) on day 0, and sacrificed on day 28. Lung tumorigenesis in F344 male rats was initiated by DHPN in drinking water for 2 weeks, and the animals were then sacrificed in week 30. Lung proliferative lesions, hyperplasias and adenomas, were observed with DHPN, and inflammation was observed with quartz. The expressions of SP-A, SP-B, SP-C and SP-D were examined immunohistochemically. SP-B and SP-C showed strong expression in lung hyperplasias and adenomas, while SP-A and SP-D were observed in mucus or exudates in inflammatory alveoli. These results suggest the possibility that SP-B and SP-C are related to lung tumorigenesis.

Napsin A expression in small cell carcinoma of the lung: a cytologic study with review of differentials

INTRODUCTION

Napsin A is a diagnostic marker for pulmonary adenocarcinoma and a useful alternative to thyroid transcription factor 1 (TTF-1). TTF-1 also stains pulmonary small cell carcinoma (SCCA). Napsin A expression in SCCAs is not as established as it is in non-SCCAs. We analyzed napsin A and TTF-1 expression in 36 previously confirmed cytologic cases of pulmonary SCCA. Ours is currently the largest cytologic series of such cases examined for napsin A expression.

MATERIALS AND METHODS

Thirty-six patients, (20 men, 16 women), age 43-87 years, mean 57 years, had primary or metastatic pulmonary SCCA diagnosed by fine-needle aspiration biopsies of mediastinum (n = 5); liver (n = 3); subcutaneous nodule (n = 1); lung (n = 6); and axillary, cervical, and mediastinal lymph nodes (n = 20), as well as a pleural effusion (n = 1). Napsin A and TTF-1 expression was tested. Also, previous expression (or lack thereof) with immunocytochemical stains pancytokeratin and neuroendocrine markers (synaptophysin, chromogranin, and cluster of differentiation marker CD56) were noted.

RESULTS

All cases of pulmonary SCCA were positive for pancytokeratin. TTF-1 was positive in 35 of 36 cases (97%), and napsin A was negative in all 36 cases (100%). All 36 cases expressed ≥ 1 neuroendocrine marker, including the TTF-1 negative case.

CONCLUSIONS

This study showed napsin A was negative in all pulmonary SCCAs. This stain may prove to be a useful exclusionary marker in distinguishing pulmonary SCCA from other poorly differentiated lung carcinomas with similar morphologic features, especially those with concomitant TTF-1 expression.

Napsin A is possibly useful marker to predict the tumorigenic potential of lung bronchiolo-alveolar hyperplasia in F344 rats

There are 2 types of bronchiolo-alveolar hyperplasia found in rat lungs. One is 'inflammatory hyperplasia' with a potential to recover in future with removal of the stimulating insult and the other is 'latent tumorigenic hyperplasia' as an independent preneoplastic lesion for adenocarcinoma. In the present experiment, we focused on rat lung bronchiolo-alveolar hyperplasia induced by 4-(methyl-nitrosamino)-1-(3-pyridyl)-1-butanone (NNK), which decreases with time after induction and reverts to normal, or by N-bis(2-hydroxypropyl)nitrosamine (DHPN), with tumorigenic potential to progress to adenoma and adenocarcinoma. Though NNK is a typical carcinogen inducing lung adenocarcinoma in female A/J mice, the tumorigenic potential by NNK in rats is weak. Differences between hyperplasias induced by DHPN and by NNK were here examined immunohistochemically. Formalin fixed paraffin embedded lung samples with hyperplastic and inflammatory lesions were obtained from rats exposed to DHPN or NNK and from lung inflammation models induced with fine particles like CuO, NiO and quartz. The 19 markers were examined immunohistochemically. Napsin A, in the inflammatory lesions and hyperplasia induced by NNK, was positive for macrophages and secretions in the alveoli spaces but less so in the walls of the alveoli. In the proliferative lesions including hyperplasia induced by DHPN, strong positive staining for napsin A was observed in the walls of the alveoli. Thus high expression was suggested to be possibly useful for detecting tumorigenic potential of rat lung hyperplasia.

Subtyping non-small cell lung cancer: relevant issues and operative recommendations for the best pathology practice

Morphology still remains the cornerstone in lung cancer classification and cytology and small biopsy samples should be interpreted by morphology, whenever feasible, according to shared and widely agreed-upon diagnostic schemes. However, as novel therapy strategies are being offered on the basis of the diverse tumor characteristics, pathologists are now challenged by the need to offer clinicians more detailed typing of non-small cell lung cancer, not otherwise specified (NSCLC-NOS), especially when dealing with limited diagnostic material or poorly differentiated tumors. Close integration of morphology, immunohistochemistry, and clinical data is highly warranted according to a multidisciplinary approach to limit the category of NSCLC-NOS as much as possible or exclude unsuspected metastases, so rendering more definite and clinically useful diagnoses. Among the many proposed immunohistochemical markers, which as a whole are more practical and diagnostically useful than cumbersome and expensive molecular assays, a 2-hit model including thyroid transcription factor-1 (TTF-1) and p40 (the latter more specific for squamous differentiation than p63) seems to be the most effective to basically highlight adenocarcinoma (positivity for TTF-1 regardless of p63) and squamous (always strongly and diffusely positive for p40 or p63 and negative for TTF-1) differentiation. This minimalist 2-hit diagnostic approach paves the way to novel perspectives in clinical trials on lung cancer, and it is also in keeping with the need of strategically preserving diagnostic material for molecular assays that are essential for personalizing therapies.