Cytologic features of functioning stromal cells in a yolk sac tumor of the ovary. A case report.

BACKGROUND Functioning stromal cells are sometimes seen in primary and metastatic ovarian neoplasms. However, the cytologic features of functioning stromal cells have been described only rarely. CASE A 19-year-old woman had an alpha-fetoprotein-producing ovarian yolk sac tumor with functioning stroma. Her preoperative serum testosterone level was elevated. Imprint cytology showed that the functioning stromal cells had centrally located nuclei with low nuclear/cytoplasmic ratios. Occasionally these cells had vacuolated cytoplasm, suggesting the presence of lipids. In sharp contrast, the yolk sac tumor cells had more pleomorphic and hyperchromatic nuclei. We were able to distinguish between neoplastic and functioning stromal cells on the basis of these findings. In addition, immunostaining for inhibin on imprint cytologic slides was of great help in identifying functioning stromal cells. CONCLUSION Because functioning stromal cells may unexpectedly induce hormonal effects in a variety of ovarian tumors, it is important to identify such cells in cytologic specimens.