Endometriotic cyst in the mesosalpinx: a case report and review of the literature.

Abstract

Endometriotic cysts often develop in the ovaries, while endometriotic nodules commonly develop in extra-ovarian sites. Herein, we report a rare case of an endometriotic cyst occurring in the mesosalpinx, and immunohistological reviews of its the pathogenesis. Magnetic resonance imaging of a 36-year-old multiparous female patient detected a 6 cm-large cyst in the right adnexal region. Likewise, a cystic tumor in the right mesosalpinx distant to the right fallopian tube and ovary, was detected via laparoscopy. On pathological examination, the inner surface of the cyst was lined with cuboidal epithelium and showed hemosiderin deposition and, thus, was diagnosed as an endometriotic cyst.Immunohistologically, it was positive for CD10 and vimentin, further supporting the diagnosis of endometriotic cyst. It was also positive for estrogen and progesterone receptors, indicative of a Müllerian-type epithelial character, and parts with positivity and negativity for the mesothelial marker calretinin were found. The calretinin-negative transition was considered to be due to a metaplastic process from peritoneal mesothelium to Müllerian-type epithelium. In conclusion, the coelomic metaplasia theory is possibly involved in the pathogenesis of endometriotic cysts located in the mesosalpinx.Detailed macroscopic findings via laparoscopy were also helpful in reaching this conclusion.