Cytologic features useful for distinguishing small cell from non-small cell carcinoma in bronchial brush and wash specimens

One blinded observer (C.D.S.) retrospectively reviewed 76 previously diagno sed and biopsy-confirmed malignant bronchial brush and wash specimens, 46 n on-small cell and 30 small cell carcinomas, obtained from 55 patients. Each case was scored for the presence or absence of 36 standard cl-iter ia (arc hitectural, cytoplasmic, and nuclear). Logistic regression analysis was use d to determine which criteria were most useful for searching small cell fro m non-small cell lesions. Although no single criterion displayed 100% sensi tivity and specificity for small cell cancer, univariate statistical analys is indicated that 3 individual criteria (nuclear molding, finely granular o r "salt and pepper" chromatin, and scant delicate cytoplasm) were more than 90% sensitive and specific in cases of small cell carcinoma. The presence of nuclear molding alone provided the best fit for the logistic regression model. When nuclear molding was present, the odds of a small cell diagnosis increased more than 300-fold. Nuclear molding, finely granular or salt and pepper chromatin, and scant, delicate cytoplasm are the 3 most sensitive a nd specific cytomorphologic features traditionally used to separate small c ell from non-small cell carcinoma. Nuclear molding alone represents the mos t significant cytomorphologic feature for distinguishing between these mali gnant lesions.