Simultaneous Occurrence of Well-Differentiated Papillary Mesothelial Tumor and Multicystic Mesothelioma

We report a rare case of simultaneous well-differentiated papillary mesothelial tumor (WDPMT) and multicystic mesothelioma. The concurrent occurrence of these entities is exceptionally uncommon and may pose challenges during surgical intervention. Both lesions are rare mesothelial proliferations that are often identified incidentally during surgery. Well differentiated papillary mesothelial tumor (WDPMT) is a neoplastic mesothelial proliferation of low malignant potential, which predominantly involves the peritoneum of young women. Microscopically it is composed of branching plump papillae lined by a single layer of bland cuboidal mesothelial cells. Cytologic atypia is minimal, and mitoses usually absent (or at most 1 mitosis per 10 high power fields). Differential diagnosis includes: 1. diffuse malignant peritoneal mesothelioma, 2. localized malignant peritoneal mesothelioma, 3. serous borderline tumors. A 41-year-old patient was admitted for laparoscopic surgery due to a tumor mass localized near the left ovary. Ultrasound examination revealed solid lesion adjacent to the left ovary, exhibiting central vascularization. The patient was diagnosed with the solid tumor mass during routine gynecological examination. The mass was extraovarian and positioned between the left ovary and the uterus. Over the course of the next 18 months, the tumor increased 5 cm in size. Given the fact that the patient presented with no symptoms, such as abdominal pain, distension or ascites, and that the tumor markers were not elevated, additional radiological imaging such as CT or MRI of the abdomen and pelvis was not performed. Intraoperatively, the mass appeared as an extraovarian solid tumor of soft consistency positioned between the left ovary and the uterus. Extirpation of the tumor was performed. Frozen section analysis of the extirpated tumor mass confirmed the diagnosis of WDPMT. During the laparoscopic procedure, a left adnexectomy was also performed and multiple biopsies of white nodules were found dispersed in the peritoneal cavity. Final patohystological analysis concluded that these nodules were peritoneal inclusion cysts. Almost three years after the procedure, the patient is without symptoms and regular clinical and ultrasound examinations were performed every six months, which showed no signs of recurrence or dissemination of the primary tumor. Recognizing well-differentiated papillary mesothelial tumor and multicystic mesothelioma is critical for accurate differential diagnosis from malignant mesothelioma. Awareness of these entities informs appropriate surgical management and follow-up protocols.