Atypical carcinoid tumor of the lung

Abstract

Human atypical carcinoid tumors (17) of the lung that are histologically intermediate between small cell undifferentiated carcinoma and typical carcinoid tumor are described. Atypical carcinoid tumors have a distinctive microscopic pattern of nests, trabeculae and ribbons of intermediate-sized, moderately pleomorphic cells that lack the nuclear molding and dense hyperchromasia of small cell undifferentiated carcinoma. Mucin was present in 15 cases and 9 contained argyrophilic granules. The 3 primary tumors and 1 metastasis studied ultrastructurally contained dense-core granules and variable degrees of squamous and glandular differentiation. Eleven patients were men; 6 were women. Their mean age was 58 yr. Sixteen patients were known smokers. Twelve tumors involved the upper lobes and 3 were located in the right middle lobe. Mean tumor size was 4.9 cm (median 4; range 2.5-20). Four of 13 patients having potentially curative resection died of tumor. The other 9 patients were disease free with a mean follow-up of 20 mo. Four additional patients treated palliatively died.