Squamous predominance in mixed-epithelial papillary cystadenomas of borderline malignancy of mullerian type arising in endometriotic cysts: A study of four cases

Mixed-epithelial papillary cystadenoma of borderline malignancy of mullerian type (MEBMM) is composed of a mixture of mullerian epithelial types, such as mucinous, serous, endo-metrioid, and squamous. Four cases of MEBMM with squamous overgrowth (MEBMMSO) were reviewed. The patients' median age was 56 years, and all cases were unilateral. The clinical stages were la (two cases), Ic (one case), and IV based on the presence of tumor cells in pleural fluid (one case). No recurrence was seen in three of the cases. In one of those three cases, there was no recurrence after undergoing surgery only; in the other two of those three cases, there was no recurrence after undergoing surgery and receiving postoperative chemotherapy. In the single case that was at stage IV at initial presentation, a recurrent MEBMMSO nodule was found at a second look 17 months after the initial surgery. In terms of gross findings, all of the tumors were cystic with intracystic papillary fronds. In addition, old endometriotic lesions lined the cysts. The tumors were mainly composed of a proliferation of squamous-type epithelium, with minor foci containing a mixture of other mullerian-type epithelia, especially mucinous. Intraepithelial infiltration by neutrophilic leukocytes was prominent. The differential diagnosis of MEBMMSO includes proliferating Brenner tumors.