Large pelvic accessory spleen mimicking an adnexal malignancy in a teenage girl.

A large pelvic accessory spleen in a teenage female is rare and may be misdiagnosed as an adnexal tumor. A 17-year-old girl, gravida 0, had suffered from intermittent and dull pain in the lower abdomen for 1 month. Laboratory evaluation showed a low platelet count (136,000/microL). Abdominal sonography showed a large solid mass situated at the right pelvis, containing abundant vascular supply with low resistant blood flow. At laparotomy, an accessory spleen fed by a tortuous vascular pedicle from the omentum was found and then excised. Histopathologic examination revealed congestive accessory splenomegaly. Follow-up platelet count returned to normal levels (374,000/microL). The importance of including accessory spleen in the differential diagnosis of a solid adnexal tumor with thrombocytopenia is emphasized.