Synchronous dual primary lung carcinomas

Synchronous dual primary lung carcinomas were found in 8 of 482 patients with lung cancer, an incidence of 1.6 percent. Of the 8 cases, 7 were unilateral and one bilateral. Three showed dissimilar histologic patterns occurring in combinations of squamous-cell carcinoma and adenocarcinoma. In 5 cases, two separate tumors were noted with identical histologic patterns in combinations of squamous-cell, giant-cell, large-cell, adeno-. and undifferentiated carcinoma. The patients were heavy smokers and this possibly may have been a factor in the development of carcinoma at more than one site.