Cytological features of alveolar cell carcinoma in sputum and direct method obtained by four patients were described and the source of exfoliated cancer cells in the airway discussed from the pathohistological standpoint. The cytological characteristics of alveolar cell carcinoma in that smear material consisted of a cluster formation of carcinoma cells with tight cellular junction and the rounded and smooth outer margin of the cell cluster.
Each cancer cell was columnar or cuboidal, the nucleus was eccentric, the nucleoli were small, and the nuclear chromatin did not marked increase. The cancer cells were uniform in shape. As exfoliated alveolar cell carcinoma clusters were observed in the normal alveolar speaces, it was considered that exfoliated cells were expectorated outward from the route via normal alveoli.
