Primary undifferentiated small cell carcinoma of the esophagus: clinicopathological and flow cytometric evaluation of eight cases. We present a clinicopathological and flow cytometric evaluation of eight primary small cell carcinomas of the esophagus representing 1.5% of all esophageal malignancies diagnosed during a 22-year period (1965-1987) in the Tampere University Central Hospital. The mean age of the patients (four male and four female) was 67 years (range 55-75 years). Five cases had distant metastases at the time of diagnosis. Three patients were treated by esophageal resection, one by laser vaporisation, and four by chemotherapy. The median survival time was 4 months (range 9 days to 8 months). A complete local response to chemotherapy in serial esophagogramms was detected in one patient. All four patients given chemotherapy survived longer than those treated with esophageal resection only. Four (67%) of the six carcinomas analyzed by DNA flow cytometry contained DNA-aneuploid stemlines. The median S-phase fraction of these small cell carcinomas was high (16.3%), reflecting rapid cell proliferation rate, which may be related to their responsiveness to chemotherapy. 