Small cell carcinoma of the lung. Prognosis in relation to histologic subtype.

Forty-six of 59 patients with small cell carcinoma of the lung who were treated with multiple drug chemotherapy and radiotherapy were subclassified according to the World Health Organization classification. Subtyping was not possible in the 13 other patients who were diagnosed on sputum cytology findings alone. There was no significant difference in extent of disease, response, duration of response to treatment, or median survival between the different subtypes. Two main difficulties arise in applying the subtyping classification. First, many tumors showed features of several histologic subtypes, implying the existence of a morphologic continuum within the general group of small cell anaplastic carcinomas. Second, tissue crushing artefact was common. Our results do not reveal any advantage in knowing the tumor subtype. It remains essential to differentiate small cell anaplastic carcinoma from other forms of lung carcinoma not responsive to chemotherapy.