Papillary lung carcinoma with prominent "morular" component.

Three cases of primary pulmonary papillary carcinomas with a prominent "morular" component involved 2 women and 1 man (age range, 25-68 years). The patients had symptoms related to the pulmonary mass, including chest pain, cough, and dyspnea. Radiographic evaluation of the thorax revealed the presence of a pulmonary mass. Surgical biopsies were obtained and reported as non-small cell carcinoma. All patients underwent lobectomy. Two tumors were located in the right upper lobe and 1 in the left upper lobe. The tumors were soft, white to tan, without evidence of necrosis or hemorrhage, and 2.5 to 3.5 cm in greatest diameter. The tumors were characterized predominantly by papillary architecture containing numerous "morules" composed of spindle cells without nuclear atypia or mitotic activity. Some morules were floating freely within papillary spaces; others seemed to detach from the papillary structures. Immunohistochemical studies of 2 tumors showed positivity for thyroid transcription factor-1, keratin, and carcinoembryonic antigen and negativity for thyroglobulin. The morules showed positive thyroid transcription factor-1 staining, weak keratin staining, and negative staining for smooth muscle actin, desmin, and HMB-45. These cases highlight an unusual phenomenon, that of primary papillary carcinomas of the lung with a prominent morular component.