A Rare Placental Site Nodule Involving the Ovary

Placental site nodule (PSN) is a benign lesion representing a nodular aggregate of intermediate trophoblast, embedded in a hyalinized stroma, thought to arise from noninvoluted placental site remaining from a past gestation. Uterus is the most common site of PSN. Occurrence in extrauterine sites is rare, with most examples being reported in the fallopian tubes. Here we report an example of PSN in the ovary. A 35-year-old woman, gravida 4, para 1, with history of adnexal ectopic pregnancy treated with methotrexate, at 39 weeks and 1 day of a subsequent pregnancy, underwent a scheduled C-section. The surgery was successful, and a healthy female infant was delivered. Intraoperative adnexal inspection revealed a small pedunculated mass on the right ovary, which was excised and sent for pathological examination. Gross inspection showed a soft, tan-white tissue fragment measuring 2.0 x 1.0 x 0.2 cm. Microscopic examination showed epithelioid cells with hyperchromatic, mildly atypical nuclei and abundant eosinophilic cytoplasm, embedded in a hyalinized stroma, forming a nodule. A diagnosis of placental site nodule was made. Immunohistochemical stains for keratin AE1/AE3, vimentin, and inhibin were strongly positive in the epithelioid cells, and immunostain for p63 was focally positive, supporting the diagnosis. PSN of the ovary is extremely rare. To our knowledge, there has been only one reported patient in the literature so far. Extrauterine PSNs are thought to arise from ectopic pregnancies. Our patient's ovarian PSN is most likely a consequence of her previous adnexal ectopic pregnancy, which was treated medically.