Mixed epidermal cyst and mucinous cystadenoma of the ovary: a hitherto unreported entity

Abstract

Epidermal (epidermoid) cyst (EC) is believed to arise from misplaced epidermis after injury or developmental anomaly of the follicular infundibulum in the skin [1]. Epidermal cyst of the ovary is extremely rare; only about 40 cases of EC have been reported [2–5]. Mucinous cystadenoma (MC) of the ovary is a very common neoplasm. The author recently encountered a case of right ovarian cyst composed only of EC and MC. This combination has not been reported, to the best of the author’s knowledge. A 37-year-old pregnant (gestational 12 weeks) woman was found to have a right ovarian cyst by imaging modalities (Fig. 1). The cyst had no solid area (Fig. 1). Right oophorectomy was performed. Grossly, the cyst was multilocular cyst containing sero-mucinous fluid (Fig. 2). No solid areas or mural nodules were seen. The cyst was white and measured 6 cm 9 6 cm 9 6 cm. Microscopically, the cyst was composed only of EC (Fig. 3) and MC (Fig. 4). Other elements were not recognized. The EC had granular layer and contained laminated keratins (Fig. 3), while MC was composed of a layer of mucous cells without atypia (Fig. 4). The EC and MC were intimately intermingled (Fig. 5). No other elements were recognized. A pathological diagnosis of mixed EC and MC was made. The patient underwent normal delivery, and is now healthy. To the best of the author’s knowledge, this is the first case of coexistence of EC and MC in the same ovary. The pathogenesis of the present case is unclear. Mucinous cystadenoma is thought to arise from surface epithelial cells. Epidermal cyst of the ovary has been thought to arise from surface epithelial cells [2] or Brenner tumor [3]. Fan et al. [4] thought that EC of the ovary is monodermal teratoma. Khedmati et al. [5] thought that EC of the ovary is heterogenous in origin, and that it arises from teratoma, Brenner tumor, and endometriosis. Mucinous cystadenoma is well known to infrequently coexist with mature cystic teratoma [6]. Other tumors reported to coexist with MC are squamous cell carcinoma [7], clear cell adenocarcinoma [8], Brenner’s tumor [9], serous cystadenoma, endometriosis cyst, granulosa cell tumor [10], carcinoid tumor [11], signet ring cells [12] and other tumors. Of these, the coexistence of MC and teratoma is the most common, but other tumors of coexisting with MC are extremely rare. Clinically, the simultaneous MC and teratoma or only MC may rupture, creating pseudomyxoma peritonei which causes serious problems [6]. The coexistence of squamous cell carcinoma or clear cell adenocarcinoma shows poor prognosis. The coexistence of Brenner’s tumor, serous cystadenoma, endometriosis cyst, granulosa cell tumor shows favorable prognosis. Endometriosis cysts may give rise to the development of clear cell adenocarcinoma or endometrioid adenocarcinoma. The coexistence of MC with carcinoid tumor has intermediate malignant potential, depending on the types of carcinoid tumor. The MC with signet ring cells [12] is a recently described entity and the biological features are unclear. The present tumor (simultaneous EC and MC) may show little clinical significance because both components were entirely benign. It is possible that other gynecologists have also observed this concurrence; however, they did not T. Terada (&) Department of Pathology, Shizuoka City Shimizu Hospital, Miyakami 1231 Shimizu-Ku, Shizuoka 424-8636, Japan e-mail: piyo0111jp@yahoo.co.jp