Neuroendocrine tumors of the lung: recent developments in histopathology

Novel Humoral Prognostic Markers in Small-Cell Lung Carcinoma: A Prospective Study

Purpose

Favourable small cell lung carcinoma (SCLC) survival outcomes have been reported in patients with paraneoplastic neurological disorders (PNDs) associated with neuronal antibodies (Neur-Abs), but the presence of a PND might have expedited diagnosis. Our aim was to establish whether neuronal antibodies, independent of clinical neurological features, correlate with SCLC survival.

Experimental Design

262 consecutive SCLC patients were examined: of these, 24 with neurological disease were excluded from this study. The remaining 238 were tested for a broad array of Neur-Abs at the time of cancer diagnosis; survival time was established from follow-up clinical data.

Results

Median survival of the non-PND cohort (n = 238) was 9.5 months. 103 patients (43%) had one or more antigen-defined Neur-Abs. We found significantly longer median survival in 23 patients (10%) with HuD/anti-neuronal nuclear antibody type 1 (ANNA-1, 13.0 months P = 0.037), but not with any of the other antigen-defined antibodies, including the PND-related SOX2 (n = 56, 24%). An additional 28 patients (12%) had uncharacterised anti-neuronal nuclear antibodies (ANNA-U); their median survival time was longer still (15.0 months, P = 0.0048), contrasting with the survival time in patients with non-neuronal anti-nuclear antibodies (detected using HEp-2 cells, n = 23 (10%), 9.25 months). In multivariate analyses, both ANNA-1 and ANNA-U independently reduced the mortality hazard by a ratio of 0.532 (P = 0.01) and 0.430 (P<0.001) respectively.

Conclusions

ANNAs, including the newly described ANNA-U, may be key components of the SCLC immunome and have a potential role in predicting SCLC survival; screening for them could add prognostic value that is similar in magnitude to that of limited staging at diagnosis.

Gene Expression Analysis of the 26S Proteasome Subunit PSMB4 Reveals Significant Upregulation, Different Expression and Association with Proliferation in Human Pulmonary Neuroendocrine Tumours

Background: Proteasomal subunit PSMB4 was suggested to be a survival gene in an animal model of hepatocellular carcinoma and in glioblastoma cell lines. In pulmonary adenocarcinoma, a high expression of these genes was found to be associated with poor differentiation and survival. This study investigates the gene expression levels of 26S proteasome subunits in human pulmonary neuroendocrine tumours including typical (TC) and atypical (AC) carcinoid tumours as well as small cell (SCLC) and large cell (LCNEC) neuroendocrine carcinomas.

Material and methods: Gene expression levels of proteasomal subunits (PSMA1, PSMA5, PSMB4, PSMB5 and PSMD1) were investigated in 80 neuroendocrine pulmonary tumours (each 20 TC, AC, LCNLC and SCLC) and compared to controls. mRNA levels were determined by using TaqMan assays. Immunohistochemistry on tissue microarrays (TMA) was performed to determine the expression of ki67, cleaved caspase 3 and PSMB4.

Results: All proteasomal subunit gene expressions were significantly upregulated in TC, AC, SCLC and LCNEC compared to controls. PSMB4 mRNA is differently expressed between all neuroendocrine tumour subtypes demonstrating the highest expression and greatest range in LCNEC (p=0.043), and is significantly associated with proliferative activity (p=0.039).

Conclusion: In line with other 26S proteasomal subunits PSMB4 is significantly increased, but differently expressed between pulmonary neuroendocrine tumours and is associated with the proliferative activity. Unlike in pulmonary adenocarcinomas, no association with biological behaviour was observed, suggesting that increased proteasomal subunit gene expression is a common and probably early event in the tumorigenesis of pulmonary neuroendocrine tumours regardless of their differentiation.

Neuroendocrine tumours--challenges in the diagnosis and classification of pulmonary neuroendocrine tumours

Pulmonary neuroendocrine (NE) proliferations are a diverse group of disorders which share distinct cytological, architectural and biosynthetic features. Tumours composed of NE cells are dispersed among different tumour categories in the WHO classification of tumours and as such do not conform to a singular group with regards to treatment and prognosis. This is reflected by the highly variable behaviour of NE proliferations, ranging from asymptomatic, for instance in diffuse idiopathic pulmonary NE cell hyperplasia and tumourlets, to highly malignant cancers such as small cell lung cancer and large cell NE carcinoma. In this review NE proliferations are described as distinct entities ranging from low grade lesions to high grade cancers. The differential diagnoses are considered with each of the entries. Finally, mention is made of tumours which may show some NE features.

Morphologic analysis of pulmonary neuroendocrine tumors

Background

Few studies on how to diagnose pulmonary neuroendocrine tumors through morphometric analysis have been reported. In this study, we measured and analyzed the characteristic parameters of pulmonary neuroendocrine tumors using an image analyzer to aid in diagnosis.

Methods

Sixteen cases of typical carcinoid tumor, 5 cases of atypical carcinoid tumor, 15 cases of small cell carcinoma, and 51 cases of large cell neuroendocrine carcinoma were analyzed. Using an image analyzer, we measured the nuclear area, perimeter, and the major and minor axes.

Results

The mean nuclear area was 0.318±0.101 µm² in typical carcinoid tumors, 0.326±0.119 µm² in atypical carcinoid tumors, 0.314±0.107 µm² in small cell carcinomas, and 0.446±0.145 µm² in large cell neuroendocrine carcinomas. The mean nuclear circumference was 2.268±0.600 µm in typical carcinoid tumors, 2.408±0.680 µm in atypical carcinoid tumors, 2.158±0.438 µm in small cell carcinomas, and 3.247±1.276 µm in large cell neuroendocrine carcinomas. All parameters were useful in distinguishing large cell neuroendocrine carcinoma from other tumors (p=0.001) and in particular, nuclear circumference was the most effective (p=0.001).

Conclusions

Pulmonary neuroendocrine tumors showed nuclear morphology differences by subtype. Therefore, evaluation of quantitative nuclear parameters improves the accuracy and reliability of diagnosis.

Respiratory Tract and Mediastinum

Normal cytology, abnormal and atypical cells, non-cellular components, and infectious cell changes are largely described together with benign, malignant, and neuroendocrine lesions regarding exfoliative and aspiration cytology of the lung. A separate section broadly addresses diagnostic findings and differential diagnoses in bronchoalveolar washings.

The section ‘Fine needle aspiration biopsy of mediastinal disorders’ covers in particular biopsy techniques, accuracy of liquid-based cytology, and the complex lesions of the thymus gland. Cytodiagnostic algorithms of the major benign and malignant pulmonary and mediastinal lesions and their respective differential diagnoses are additionally presented in synoptic setups.

Small cell carcinoma of the lung and large cell neuroendocrine carcinoma interobserver variability

AIMS

To test the hypothesis that the published morphological criteria permit reliable segregation of small cell carcinoma of the lung (SCLC) and large cell neuroendocrine carcinoma (LCNEC) cases by determining the interobserver variation.

METHODS AND RESULTS

One hundred and seventy cases of SCLC, LCNEC and cases diagnosed as neuroendocrine lung carcinoma before LCNEC had been established as a diagnostic category were retrieved from the archives of the assessor's institutes. A representative haematoxylin and eosin section from each case was selected for review. Batches of cases were circulated among nine pathologists with a special interest in pulmonary pathology. Participants were asked to classify the cases histologically according to the 2004 World Health Organization (WHO) criteria. The diagnoses were collected and kappa values calculated. Unanimity of diagnosis was achieved for only 20 cases; a majority diagnosis was reached for 115 cases. In 35 cases no consensus diagnosis could be reached. There was striking variability amongst assessors in diagnosing SCLC and LCNEC. The overall level of agreement for all cases included in this study was fair (kappa=0.40).

CONCLUSIONS

Using non-preselected cases, the morphological WHO criteria for diagnosing SCLC and LCNEC leave room for subjective pathological interpretation, which results in imprecise categorization of SCLC and LCNEC cases.

Pulmonary Neuroendocrine Tumors

Pulmonary neuroendocrine tumors are frequently encountered as small biopsy and resection specimens. Although the World Health Organization (WHO) classification is used as a diagnostic framework globally and in daily practice, it is not without controversy and practical difficulties. The WHO criteria for pulmonary neuroendocrine tumors are reviewed with the recognition that the definitions are based on resected specimens, which are often not the usual clinical circumstances. A practical approach is emphasized, and the differential diagnosis is discussed with particular attention to the context in which diagnostic difficulties are most frequently encountered, such as small biopsies and frozen sections.

Neuroendocrine carcinomas of the lung: a critical analysis

Neuroendocrine carcinomas represent an important group of primary neoplasms in the lung. During the last decades, the nomenclature of these tumors has evolved and the current use of immunohistochemical and molecular biology studies have, to some extent, expanded the conventional view of these tumors. However, the primary diagnosis of most of these lesions is performed on limited biopsy specimens, which may not translate well when one is confronted with a nomenclature that is based on resected material. In addition, for some of these specific entities, some confusion and controversy apparently remain, allowing for the proliferations of different terms that, although they may be dismissed as "semantics," may have a role in interpretation, further subclassification, and, possibly, treatment. Herein we review current concepts regarding the classification of these neoplasms and the role of this classification in our daily practice and discuss how it may impact treatment.

Expression of amino acid sequences of the chromogranin A molecule and synaptic vesicle protein 2 in neuroendocrine tumors of the lung

Chromogranin A (CgA) and its valuable complement synaptic vesicle protein 2 (SV2) are neuroendocrine (NE) markers. Post-translational processing of CgA has been reported to vary in different NE cell types and tumors, but little is known regarding the expression of various CgA epitopes and SV2 in NE pulmonary tumors. We studied the immunoreactivity to six CgA epitopes and SV2 in ten typical (TC) and ten atypical (ACT) carcinoids, five large-cell NE carcinomas (LCNEC) and five small-cell carcinomas (SCLC), also comparing the results with clinicopathological characteristics of tumors. The sequences CgA 17--38 (vasostatin), 176--195 (chromacin), 375--384 (parastatin) and 411--424 (C-terminal parastatin) and SV2 were relevant markers for the CT/ATC group, whereas the antibody to CgA 176--195 was a better marker for the LCNEC/SCLC group. An inverse correlation was found between proliferative activity and granule-related markers in the CT/ACT group, and a direct correlation in poorly differentiated tumors. The expression of granule-related markers did not correlate with hormone content or clinical characteristics of NE tumors. The expression of CgA epitopes and SV2 occurs in all NE tumors, differing between better differentiated and poorly differentiated tumors but not within the respective groups.

Typical and Atypical Pulmonary Carcinoid Tumor Overdiagnosed as Small-Cell Carcinoma on Biopsy Specimens

Seven patients with typical or atypical pulmonary carcinoid tumors overdiagnosed as small-cell carcinoma on bronchoscopic biopsies are described. Bronchial biopsies from 9 consecutive small-cell lung carcinoma patients were used as control group for histologic and immunohistochemical studies (cytokeratins, chromogranin A, synaptophysin, Ki-67 [MIB-1], and TTF-1). The carcinoid tumors presented as either central or peripheral lesions composed of tumor cells with granular, sometimes coarse chromatin pattern, high levels of chromogranin A/synaptophysin immunoreactivity, and low (<20%) Ki-67 (MIB-1) labeling index. The tumor stroma contained thin-walled blood vessels. Small-cell carcinomas always showed central tumor location, finely dispersed nuclear chromatin, lower levels of chromogranin A/synaptophysin, and high (>50%) Ki-67 (MIB-1) labeling index. The stroma contained thick-walled blood vessels with glomeruloid configuration. Judging from this study, overdiagnosis of carcinoid tumor as small-cell carcinoma in small crushed bronchial biopsies remains a significant potential problem in a worldwide sample of hospital settings. Careful evaluation of hematoxylin and eosin sections remains the most important tool for the differential diagnosis, with evaluation of tumor cell proliferation by Ki-67 (MIB-1) labeling index emerging from our review as the most useful ancillary technique for the distinction.

Molecular markers for reinforcement of histological subclassification of neuroendocrine lung tumors

The degree of malignancy of neuroendocrine lung tumors (NEs) increases in this order: from typical carcinoids (TCs) through atypical carcinoids (ACs) to large cell neuroendocrine carcinomas (LCNECs) and small cell lung carcinomas (SCLCs). However, histological classification has sometimes proved difficult. We here investigated loss of heterozygosity (LOH) using eight microsatellite markers and expression of p53, Bcl-2 and Bax proteins using immunohistochemical methods in 57 NEs (19 TCs, 5 ACs, 14 LCNECs and 19 SCLCs), looking for objective genetic markers to distinguish between subtypes. The frequencies of LOHs on D3S1300, RBi2 and TP53, the combinations of LOH status for RBi2 and TP53, and the immunohistochemically demonstrated Bcl-2/Bax ratios and p53-positive rates significantly differed among histopathologically diagnosed NEs. Differentiation between TC and AC was possible with reference to LOH on D3S1300, RBi2 and TP53, and the combined LOH status on RBi2 and TP53 (i.e., both LOH(-) versus one LOH(+)). For comparison between AC and LCNEC + SCLC, LOH on TP53 or the combination of two markers--one LOH(+) versus both LOH(+)--was applied. Furthermore, in three discordant cases of diagnoses based on histology and LOH markers, diagnoses using the latter were considered to be more probable by survival analysis. The present study indicated that assessment of LOHs using microsatellite markers could provide objective markers that can distinguish subtypes of NEs, for which histological assessment may commonly result in disagreement.

Treatment of carcinoid of the lung

PURPOSE OF REVIEW

Pulmonary carcinoids are rare neuroendocrine malignancies that comprise 2% of primary lung tumors. During the last few years, important information has appeared in the literature in relation to the histopathology, molecular biology, biologic behavior, and treatment of these tumors.

RECENT FINDINGS

Histologic subclassification of carcinoid tumors into atypical and typical is of paramount importance. Genetic changes in these subclasses are now well-known and are helpful for the differentiation. The biologic behavior of typical and atypical carcinoids is completely different, and treatment planning is based on this information. Surgery is the treatment of choice for localized carcinoid tumors and includes lymphadenectomy. In metastatic disease, chemotherapy with a cisplatin-based or streptozotocin-based combination is moderately effective. Palliation with biotherapy including interferon, somatostatin analogs, and octreotide is encouraging. Liver embolization is an option for symptomatic liver involvement.

SUMMARY

Pulmonary carcinoids are rare tumors, and our understanding of their histopathology and biologic behavior are the most important factors for treatment planning. Surgery is the treatment of choice for cure.

Diagnosis and treatment of carcinoid tumors

Carcinoid tumors belong to the family of neuroendocrine tumors, which are usually slow growing with distinct biological and clinical characteristics. The incidence of these tumors is approximately 2.5 in 100,000 people per year. The former classification system of foregut, midgut and hindgut tumors is still used in clinical routine, although there is a new World Health Organization classification. Determination of the histopathology of carcinoid tumors is of utmost importance and involves specific immunohistochemical staining for chromogranin A, synaptophysin, serotonin and gastrin. Proliferation capacity measured by Ki67 is used to guide forthcoming medical treatment. Localization procedures include computerized tomography, ultrasound, magnetic resonance imaging, somatostatin receptor scintigraphy and positron emission tomography. Surgery remains the cornerstone of treatment and provides the only chance of a cure. Other cytoreductive procedures include radiofrequency ablation, laser treatment and chemoembolization. Biological treatment includes cytotoxic agents, such as somatostatin analogs and interferon-alpha, which should be applied in slow-growing neoplasms. Combination regimens including cisplatin, etoposide, streptozotocin and 5-fluorouracil should be reserved for treatment of highly proliferating tumors. Future therapy of carcinoid tumors will be based on the specific tumor biology and treatment will be customized for each individual patient. New therapies, such as antiangiogenic agents and new, long-acting somatostatin analogs, together with further development of tumor-targeted treatments, will come into clinical use in the near future.