The nucleolar findings of pulmonary cancer cells stained supravitally with brilliant cresyl blue were analysed with regard to their histological types.
1) Following Kimura's classification, the nucle oli in the cells of squamous cell carcinoma were of types R (especially R1) and C (especially C1 and C3); adenocarcinoma, type C (especially C3 and C2) and undifferentiated carcinoma, type C (especially C1 and C3). The nucleoli of non-malignant cells were of type R (especially R1 and R3).
2) Squamous cell carcinoma cells had 1 to 3, round or irregular shaped, medium or small sized nucleoli, adenocarcinoma cells had 1 or 2 round, medium or large sized nucleoli, and undifferentiated carcinoma cells had 1 to 3 round, medium or small sized nucleoli.
