Florid cystic endosalpingiosis associated with a retroperitoneal leiomyoma mimicking malignancy: a case report.

Florid cystic endosalpingiosis (FCE) is a rare type of endosalpingiosis that presents as a mass-like lesion. Here we report an unusual case of FCE associated with a retroperitoneal leiomyoma. A 46-year old female presented with a palpable abdominal mass. A pelvic CT revealed a 23.5×16.3×9.4 cm sized multilocular cystic and solid mass in the retroperitoneum. Surgical excision of the mass was performed. Microscopically, the cystic spaces were lined by a single layer of ciliated tubal epithelium. The solid areas consisted of thick bundles of spindle cells. There were no cytologic atypia, mitosis or necrosis. The spindle cells were positive for actin and desmin, and were negative for c-kit, CD34, S100 and HMB-45, confirming the diagnosis of FCE associated with retroperitoneal leiomyoma.