Cytomorphometric analysis of small cell neoplasms of the lung from specimens obtained via bronchoscopy.

Primary neoplasms of the lung composed of small cells consist of undifferentiated small cell carcinoma (UCS), carcinoid tumors (CT) and some non-small cell carcinomas (NonSC) that lack cytoplasmic differentiation. The cytologic identification of tumors from specimens obtained via bronchoscopy sometimes presents difficulties due to overlapping patterns. In order to define additional differentiating criteria, we evaluated Papanicolaou-stained smears from 30 histologically proven cases, 10 from each of the three groups, with statistical analysis of computer-assisted morphologic measures. We identified significant differences between NonSC versus USC and NonSC versus CT with regard to nuclear and cytoplasmic dimensions (P less than .0001) but not between USC and CT. The nuclear:cytoplasmic ratios were similar in all three groups (P = .39). From this preliminary study we conclude that morphometric analysis can distinguish NonSC from USC and CT but not USC from CT.