The prognostic significance of histopathologic subtyping of small cell carcinoma of the lung according to the classification of the World Health Organization. A study of 375 consecutive patients.

Three hundred seventy-five consecutive patients treated with intensive chemotherapy in the same institution are included in this study in order to evaluate the prognostic significance of the World Health Organization's (WHO) subclassification of small cell lung cancer. Morphologic subtyping, based on primary biopsy specimens, was obtained in 200 patients. Oat cell type was diagnosed in 106 patients (53%), while intermediate subtype was diagnosed in 93 patients (47%), including 27 patients (14%) with small cell/large cell morphologic features. One patient had combined oat cell type. No difference in survival period was observed between the group of patients classified as oat cell versus the group with intermediate subtype. However, a significantly shorter survival period was demonstrated for patients with small cell/large cell features compared with patients with pure small cell carcinoma (median 168 days versus 280 days, P less than 0.01). It is concluded that there is no difference in survival period between patients with oat cell and intermediate subtype of small cell lung cancer using the criteria of the WHO. However, it might be of prognostic importance to identify patients with tumors demonstrating small cell/large cell features.