Endobronchial adenocarcinoma with endometrioid features and prominent neuroendocrine differentiation. A variant of fetal adenocarcinoma.

Abstract

An endobronchial tumor, resected from a 77-year-old man, had an endometrioid histologic pattern consistent with fetal adenocarcinoma. A distinctive feature of the neoplasm was prominent neuroendocrine differentiation, including single, discrete neuroendocrine cells; aggregates of neuroendocrine cells resembling miniature carcinoid tumors; and a single focus of undifferentiated small cell carcinoma. Immunohistochemical staining of neuroendocrine cells revealed the presence of neuron-specific enolase, chromogranin, somatostatin, insulin, and serotonin. The heterogeneous cell populations caused problems in differential diagnosis and histologic classification. This case demonstrates that fetal adenocarcinoma may occur as a central endobronchial mass and express a variable degree of neuroendocrine differentiation.