Sputum cytology of metastatic carcinoma of the lung.

The cytopathology of 47 cases of metastatic carcinoma of the lung and of 28 cases of recurrent or metastatic bronchogenic carcinoma is reviewed. The diagnostic yield was better for recurrent than for metastatic carcinoma but overall was comparable to that of primary bronchogenic carcinomas. The metastatic tumors were located in all areas of the lung and included single as well as multiple lesions. The positive yield did not differ significantly in relation to any of the pathologic features but was somewhat higher if the metastases were large and centrally located. A definite differentiation of the metastatic tumors, usually adenocarcinomas, from new primary bronchogenic carcinomas is often possible particularly if the cytopathology can be compared with that of the primary lesion. Specific cytologic features include the relative lack of cohesion and the formation of columns in metastatic breast carcinomas, the formation of larger cohesive well circumscribed nodules composed of tall columnar cells in metastatic colon carcinomas, clear cell features in some metastatic adenocarcinomas of the kidney, and the small cell size and uniform, regular nuclear features in the often cytologically well differentiated metastatic carcinomas of the prostate.