Large cell neuroendocrine tumors of the lung. Clinical significance and histopathologic definition.

Twenty-five cases of neuroendocrine tumors of lung, including bronchial carcinoids (eight), malignant (atypical) carcinoids (nine), and large cell undifferentiated carcinomas (LCAC) with neuroendocrine differentiation (eight) were analyzed. All carcinoids (BC) could be diagnosed by light microscopy; all patients with these tumors are alive without disease. Five of nine malignant carcinoids (MC) could be recognized histologically; four of nine were called LCAC and required electron microscopy for diagnosis. Survival correlated best with stage of diagnosis. High-grade neuroendocrine carcinomas (LCAC-NE) required electron microscopy for their diagnosis. Seven were LCAC histologically; one was diagnosed as malignant carcinoid (MC). Such tumors resemble small cell anaplastic carcinomas ultrastructurally and behaviorally. All eight patients with such high-grade tumors died of their disease; three of eight had no nodal metastases at the time of resection. This experience suggests it is clinically important to distinguish neuroendocrine neoplasms since behavior is predictable on the basis of morphology.