Meningeal carcinomatosis from small cell carcinoma of the lung. Consequence of improved survival.

The cells of oat cell carcinoma of the lung can be identified in sputum because of their characteristic morphologic appearance. The cells from oat cell carcinomas can also be identified in other body fluids but are seen there less often. Spinal fluid involvement with oat cell carcinoma has been seen very infrequently, presumably because of a poor survival rate. Aggressive systemic chemotherapy has improved survival, and meningeal involvement is now being recognized as a complication. Of 62 patients treated by aggressive chemotherapy protocols, six (10%) were found to have leptomeningeal involvement by cytologic evaluation of cerebrospinal fluid (CSF). Involvement was found 6 to 13 months after the initiation of therapy. Two of the six patients had no evidence of CNS metastases by CAT brain scan. Necropsy was performed in three of the six cases and showed excellent histologic correlation with the cytologic findings. Because of most therapeutic drugs' poor penetration into the CSF, and because the spinal cord is not routinely irradiated, cytologic examination of the CSF from patients with oat cell carcinoma is necessary when there are new neurologic signs or symptoms to ensure proper, specific therapy.