Cytologic assessment of tumor cell kinetics: Applications of monoclonal antibody Ki‐67 to fine‐needle aspiration smears

Rates of tumor-cell proliferation often provide prognostic information about a given neoplasm. Previously available methods for accessing cell kinetics are time consuming and expensive, and often require special equipment or radioactive reagents. Monoclonal antibody Ki-67 binds a nuclear antigen expressed in proliferating but not in resting cells. We studied Ki-67 immunostaining of fine-needle aspiration smears from 40 benign and malignant masses. Labeling indices ranged from 0 (thyroid follicular adenoma) to 75 percent (pulmonary oat-cell carcinoma). Frozen section immunostaining (11 cases) and flow cytometric assessment of cell proliferation (8 cases) were in good agreement with Ki-67 labeling indices on smear material. We suggest that this method provides a rapid, inexpensive, and dependable means of assessing tumor-cell kinetics in cytologic preparations.