Abstract

Two cases of pulmonary atypical carcinoid tumor were diagnosed by fine needle aspiration cytology. Although the cytologic features of atypical carcinoid tumor have been relatively well described, it is easy to confuse atypical carcinoid tumor with typical carcinoid tumor, small cell carcinoma and adenocarcinoma of the lung. Atypical carcinoid tumor has been recognized as a distinct variant of pulmonary neuroendocrine carcinoma, with characteristic histopathologic and clinical features that separate it from both carcinoid and small cell carcinoma. The distinction of atypical carcinoid tumor from small cell carcinoma has important prognostic and therapeutic implications. The cytologic characteristics of atypical carcinoid tumor included polygonal to fusiform cells with a variable amount of lacy cytoplasm, oval nuclei with coarsely dispersed chromatin and frequent nucleoli, and mild pleomorphism. The malignant cells were arranged either in acinus-like clusters or in epithelial sheets.

• Keywords: Atypical carcinoid tumor;Lung;Fine needle aspiration cytology