To our knowledge, familial occurrence of small-cell carcinoma of the o
vary in first-degree relatives has not been described before. We studi
ed two separate cases of small-cell carcinoma in a 21-year-old patient
and in her 40-year-old mother, both of whom died of disseminated dise
ase. Both tumors were studied with immunohistochemistry, using a varie
ty of antibodies, and with flow cytometry. Microscopically, the tumor
in the daughter was of the usual small-cell type, while that of her mo
ther belonged to a large-cell variety. Immunohistochemically, both tum
ors showed some degree of epithelial differentiation but also expresse
d reactivity to some other antigens, most notably to smooth-muscle act
in and muscle-specific actin. Both tumors showed a diploid DNA pattern
and low S-phase fraction with flow cytometry. Neither of the cases ex
pressed hypercalcemia. Small-cell carcinoma of the ovary may appear as
a small-cell or large-cell variety in a familiar setting. A diploid D
NA pattern appears to be characteristic. Because this tumor was first
reported relatively recently, the frequency of its familial occurrence
is not known.