Neuroendocrine tumors are a unique malignant neoplasm that can arise from the respiratory tree. Although well-differentiated bronchial neuroendocrine tumors (also called carcinoid tumors) are reported to account for approximately 25% of all neuroendocrine tumors, they represent only 1% to 2% of all lung cancers. The epidemiology, clinical behavior, and treatment of neuroendocrine carcinoid tumors differ significantly from other lung malignancies. In this article, the recent data regarding these tumors were reviewed with attention to the treatment modalities used. Although conventional cytotoxic therapy has not been reported to demonstrate much promise in this entity over the past 4 decades, newer molecular targeted agents including those that targeted angiogenesis and the mammalian target of rapamycin (mTOR) Well-differentiated neuroendocrine, or carcinoid, tumors are a unique class of malignancies capable of producing hormones identical to those from the nervous system. Although the first carcinoid tumor described was in the ileum, neuroendocrine malignancies are a family of malignancies found throughout the body. Tumors of the bronchial tree in particular account for approximately 25% of all well-differentiated neuroendocrine tumors (Table 1). [1][2][3] However, compared with other malignancies of the bronchoalveolar tree, these well-differentiated neuroendocrine tumors are rare, accounting for only 1% of all lung cancers. 3 The pathologic spectrum of neuroendocrine malignancies ranges from low-grade carcinoid to aggressive small cell lung cancer. The low-grade and intermediate-grade neuroendocrine malignancies, also known as typical and atypical carcinoid, will be the focus of this review. The distinct features of this malignancy include its pathologic characteristics, clinical behavior, epidemiology, prognosis, and treatment.

The diagnosis of serous microcystic adenoma (SMA) is usually straightforward. For small biopsies and/or unusual variants, the differential diagnosis includes other pancreatic or metastatic neoplasms showing cystic or clear cell features. We evaluated immunostains for potential use in the diagnosis of SMA. Cases of SMA were identified from archival files. Tissue cores (2 per block) were arrayed to create a microarray of cores measuring 2mm each. Additionally, microarrays previously constructed from 56 pancreatic adenocarcinomas (PACs) and 64 pancreatic endocrine tumors (PENs) were studied. The microarrays were stained with calponin, chromogranin, CD10, alpha-inhibin, and monoclonal neuron-specific enolase (m-NSE). Subsequently, some were stained with MUC6, melan-A, D2-40, h-caldesmon, smooth muscle actin, and smooth muscle myosin. For SMAs, staining was seen with calponin (85.2%), alpha-inhibin (96.2%), and m-NSE (96.2%). Focal weak staining was seen with MUC6 (65%). All SMAs were negative with chromogranin, CD10, melan-A, D2-40, h-caldesmon, smooth muscle actin, and smooth muscle myosin. In contrast, calponin was negative in all PACs and PENs. Staining for alpha-inhibin was absent in PACs and present in 4.1% of PENs; whereas immunoreactivity for m-NSE was present in 26.8% of PACs and 73.7% of PENs. Chromogranin staining was present in 9.1% of PACs and 100% of PENs. An immunohistochemical profile of staining with calponin, alpha-inhibin, and m-NSE and absent staining with chromogranin supports the diagnosis of SMA, and distinguishes SMA from PAC and PEN. Calponin and alpha-inhibin are the most useful positive markers for SMA, and are negative in most entities in the differential diagnosis.

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