[Pathology of lung neuroendocrine tumors]

The heterogeneous group of lung neuroendocrine tumors are divided into four main types: typical carcinoid (TC), atypical carcinoid (AC), large cell neuroendocrine carcinoma (LCNEC), and small cell carcinoma (SCLC). Classification is based on the analysis of surgical resection specimens, which, in addition to basic morphological features, takes into account the mitotic count in 2 mm², the presence or absence of necrosis. According to prognosis, TC is low grade, AC is intermediate grade, while SCLC and LCNEC are high grade carcinomas with very poor prognosis. The morphological diagnosis can be refined by the use of neuroendocrine immunohistochemical markers. Based on the histological diagnosis, clinical prognosis is not always clear. Application of Ki-67 labeling can get closer to real biological behavior. Recently, more than 2/3 of the cases are small samples (core biopsy, bronchoscopic biopsy, cytological smears). Diagnostic algorithms developed for resection specimens has limited usage for these samples. In a single case, a wide range of histological techniques should be used in the processing of the sample, and still only an unsatisfactory result is obtained. Knowing the potential information content of the samples can help the clinician to set up a diagnostic and therapeutic plan.