Lung cancer heterogeneity: a blinded and randomized study of 100 consecutive cases.

The heterogeneity of lung carcinomas was recognized in the past, but few previous studies attempted to quantitate this heterogeneity. In the present study 100 consecutive cases of lung carcinoma (65 surgical resections and 35 autopsies) were collected, and either the entire tumor or ten blocks were examined in a blinded and randomized fashion using the revised (1981) WHO classification. At least three of five panelists agreed on the major histologic type present for 94 per cent of the slides. Agreement for the diagnosis of small cell carcinomas (at least four of five observers) was 98 per cent, but only 72 per cent agreement was attained for the subtyping of small cell carcinomas (e.g., oat cell versus intermediate). Only 34 per cent of the cases were homogeneous according to the majority of the panelists. An additional 21 per cent of the cases showed minor (subtype) heterogeneity (e.g., mixtures of acinar and papillary patterns in adenocarcinoma). Forty-five per cent of the cases showed major heterogeneity, i.e., at least one slide from the case showed a major histologic type different from that of the remainder. Seven small cell carcinomas were homogeneous, whereas in eight cases mixtures of small cell and other cell types were seen. In all but one of the cases involving bronchioloalveolar cell patterns, other patterns of adenocarcinoma were present elsewhere in the tumor. In all six cases involving giant cell carcinoma patterns, adenocarcinoma patterns were also present in some sections. Heterogeneity was identified by extensive sampling of the entire tumor and was seldom recognized in biopsy specimens.