DNA content and proliferative activity in ovarian small cell carcinomas of the hypercalcemic type. Implications for diagnosis, prognosis, and histogenesis.

Ovarian small cell carcinoma of the hypercalcemic type is a rare cancer of young women of nuclear histogenesis. Although usually lethal, a subset of patients with stage I tumors have survived. Twenty-five cases of small cell carcinoma (17 stage I, 1 stage II, and 7 stage III) were evaluated by flow cytometric analysis performed on paraffin-embedded tissue. Forty classifiable histograms from 23 cases were DNA diploid; histograms from two cases could not be interpreted. The mean S-phase fraction was 10.5% (4.7% to 18.4%), and the mean G2/M fraction was 5% (1.5% to 19.5%) in 22 cases. Mean values of mitotic rate, S-phase fraction, G2/M fraction, and proliferation index (%S + %G2/M) were not associated with stage or outcome, nor did any proliferation variable correlate with interval to death. A comparative review of flow cytometric findings in other types of ovarian cancer that may be confused with small cell carcinoma indicates that flow cytometry is an objective diagnostic aid to distinguish small cell carcinoma of the hypercalcemic type from other forms of small cell carcinoma, malignant germ cell tumors, and sex-cord tumors, and that small cell carcinoma probably does not belong in either the surface epithelial or germ cell categories of ovarian cancer. Finally, the flow cytometric findings in this report exemplify the rare phenomenon of a diploid DNA content in a very lethal tumor and indicate that an accurate diagnosis of tumor type is essential before a prognosis on the basis of flow cytometric data can be made.