An unusual second primary tumor. Report of a case of atypical carcinoid of the lung.

This case report presents a rare occurrence of two primary tumors in the same patient: a transitional cell carcinoma of the bladder and an atypical carcinoid of the lung. The time interval between a linear density and tumor growth to 3 cm, determined by chest radiographs, was 9 months. The rapidly growing pulmonary nodule was suspected to be a metastasis from the primary transitional cell carcinoma. Fine-needle aspiration revealed malignant cells. Lobectomy and light and electron microscopy revealed an atypical carcinoid. The definition of "atypical" requires revision to indicate this tumor's true potential.