LOCALIZED AND DIFFUSE MESOTHELIOMAS OF THE GENITAL-TRACT AND PERITONEUM IN WOMEN - A CLINICOPATHOLOGICAL STUDY OF 19 TRUE MESOTHELIAL NEOPLASMS, OTHER THAN ADENOMATOID TUMORS, MULTICYSTIC MESOTHELIOMAS, AND LOCALIZED FIBROUS TUMORS

Peritoneal mesotheliomas are rare in women, compared to serous epithel ial neoplasms with which they are often confused. We evaluated the cli nicopathologic features of 19 true mesothelial neoplasms affecting the genital tract or peritoneum of women (other than adenomatoid tumors, benign multicystic mesotheliomas, and localized fibrous tumors) to cha racterize their clinicopathologic features and to determine their clin ical behavior. Six tumors were localized to one anatomic site at prese ntation, and 13 involved more than one anatomic site. The six localize d tumors were solitary, small (0.8-2.0 cm), polypoid or nodular lesion s, five of which were incidental findings. All had a predominantly tub ulopapillary pattern, either pure or mixed with adenomatoid-like or sm all solid foci. Nuclear grade ranged from 0 to 2. Mitotic figures (MF) were absent in two tumors. The mitosis count in the other four tumors was <1 MF/10 high-power microscopic fields (HPF) (average method) and ranged from 1 to 3 MF/10 HPF (highest count method). Five patients we re alive without recurrence after postoperative intervals ranging from 19 months to 9 years (median, 5 years); one patient died of metastati c gastric carcinoma at 14 months. Thirteen tumors involved more than o ne anatomic site and were classified as diffuse mesothelioma. Typicall y, these tumors were symptomatic and accompanied by ascites. The tumor s had either a plaque-like or endophytic configuration. Eleven were pu rely epithelial mesotheliomas, and two had a minor sarcomatoid compone nt. Tubulopapillary patterns were present in 10 tumors, usually admire d with focal adenomatoid-like or solid patterns, and three had a purel y solid pattern. All 13 tumors had grade 3 nuclei. The mitosis count r anged from <1 to 2 MF/10 HPF (average count method) with a range of 1- 4 MF/10 HPF by the highest count method. Immunohistochemically, 13/13 tumors stained for cytokeratin (AE1/AE3). None were immunoreactive for polyclonal carcinoembryonic antigen (CEA), Leu-M1, or B72.3. One diff use mesothelioma stained focally for Ber-EP4, and electron microscopy confirmed the mesothelial nature of this tumor. Nine patients died of tumor after postoperative intervals ranging from 1 month to 6 years. E leven patients had received postoperative adjuvant intraperitoneal or systemic chemotherapy. One patient died with increased abdominal girth 8 years after operation and one course of intraperitoneal chemotherap y, though the role of mesothelioma in her death was uncertain. One pat ient was alive with diffuse tumor and persistent ascites 25 months aft er six courses of intraperitoneal chemotherapy. One patient was alive without evidence of disease 4 months after two courses of systemic che motherapy. One patient developed a recurrence 4 years following resect ion and six courses of intraperitoneal chemotherapy but was subsequent ly lost to follow-up. We conclude that (a) mesotheliomas affecting the genital tract and peritoneum in women, although rare, can be reliably distinguished from serous epithelial tumors; (b) clinically benign me sotheliomas are typically asymptomatic, incidentally discovered solita ry tumors which are polypoid or nodular, small (2.0 cm or less), purel y of epithelial type, with a predominant tubulopapillary pattern and g enerally low-grade nuclei; (c) clinically malignant mesotheliomas typi cally are symptomatic lesions which involve multiple sites, are associ ated with ascites, and have high-grade nuclei, though some tumors have foci with histologic features which overlap with clinically benign tu mors.