Rapid Growth of Pelvic Cyst during Pregnancy: A Case Report

Abstract

We describe a patient with bilateral cystic tumors of the pelvis. The left one rapidly grew during pregnancy and combined with the right one, whose clinical course made diagnosis difficult. A pregnant woman with a history of laparotomy was referred to us due to suspected bilateral pelvic cysts. The left-sided cyst had rapidly grown to 27 cm in diameter and merged with the right cyst, forming a large cyst occupying the entire pelvic cavity in the third trimester. Considering this rapid growth, cesarean section and resection of the cyst were performed at 37th week. The resected cyst consisted of two components: a large unilocular cyst containing serous fluid and a multilocular cyst suggestive of ovarian mucinous cystadenoma in the right ovary. The wall of the former largely lacked lining epithelium, but it was partly continuous with the latter mucinous epithelium. Immunohistochemically, estrogen and progesterone receptors were focally positive in the cyst wall, suggesting that pregnancy-associated sex-hormones may have contributed to the rapid growth of the cyst. We diagnosed this condition as a peritoneal inclusion cyst margining with a right ovarian mucinous cystadenoma. Peritoneal inclusion cyst should be considered in the differential diagnosis of a rapidly growing pelvic mass during pregnancy.

Figure 1

T2-weighed magnetic resonance imaging at 9 (a, b) and 32 (c, d) weeks of gestation. (a) Bilateral pelvic masses with a horizontal view. A right-sided multilocular mass (arrow) and left-sided unilocular mass (asterisk) are shown. We suspected bilateral ovarian tumors at this point. (b) Sagittal view. The left-sided unilocular mass (asterisk) is shown. (c) Horizontal view. The right-sided multilocular mass (arrow) is involved in or at least is located very close to the large mass (star). (d) Sagittal view. The left-sided mass (star) occupies the pelvic cavity.

Figure 2

Intra-operative findings during cesarean section (CS) and tumor resection at 37 weeks of gestation. (a) The large cyst (arrow) is on the dorsal and caudal sides of the uterus (star) following CS. (b) The large cyst wall (arrow) is adjacent to the right multicystic ovarian tumor (arrowhead). We resected the right adnexa and a part of the cyst wall. The wall of the large cyst was coarse and weak, suggestive of degeneration. Uterus (double arrows).

Figure 3

Histological findings of the right ovarian tumor (a-d). (a) The epithelium of the right ovarian tumor without dysplasia contains mucin. It is consistent with mucinous cystadenoma (Hematoxylin and Eosin stain, x20). (b) The large cyst wall containing serous fluid shows partial defects of epithelium. This is due to adhesion of the abdominal cavity and cyst. (c-e) The large cyst wall is strongly positive, partly weakly positive (arrows), and partly positive (arrowheads) for cytokeratin AE1/AE3, estrogen receptors (ER), and progesterone receptors (PR), respectively (x20).

Figure 4

Schematic presentation of enlargement of the inclusion cyst. (a) At 9 weeks, the right mucinous cystadenoma and left cyst (later diagnosed as an inclusion cyst) existed independently. (b) During gestation progressing, the inclusion cyst became larger. The right ovarian cyst and inclusion cyst became close. (c) Finally, the right ovarian cyst was involved in the inclusion cyst. Mucin-producing cells were observed mainly on the near-side of the right ovarian cyst. The wall of the inclusion cyst was largely destroyed due to inflammation, which made it difficult to conduct a detailed histological examination such as the confirmation of mesothelial cells in the inclusion cyst wall.