Malignant mesotheliomas presenting as ovarian masses. A report of nine cases, including two primary ovarian mesotheliomas.

Nine cases of malignant mesothelioma (MM) presenting as ovarian masses occurred in female patients aged 16 to 63 (median, 52) years. In most of the cases, the referring pathologist initially misdiagnosed the neoplasm or was uncertain about its nature. In two cases, the tumors were confined to one or both ovaries, representing primary ovarian MMs; only one similar case has been previously reported. In the other cases, widespread peritoneal tumor precluded definite conclusions about the primary or secondary nature of the ovarian involvement. That at least some of the latter were also primary ovarian MMs is suggested by a degree of ovarian enlargement, the striking parenchymal replacement, or both, which are not usually seen in cases of secondary ovarian involvement by peritoneal MMs. The clinical presentation was usually that of abdominal or pelvic pain or abdominal swelling, an adnexal mass on pelvic examination or at laparotomy, or combinations thereof. One tumor was an autopsy finding. There was no history of asbestos exposure in any patient. Eight patients underwent bilateral oophorectomy, usually with hysterectomy and biopsies of extraovarian tumor. Four patients were given chemotherapy and one, radiation therapy. Follow-up in five cases revealed that three patients had died of tumor at postoperative intervals of 8 to 44 months, one was alive with persistent tumor at 18 months, and one was alive with no clinical evidence of tumor at 11 years. The ovaries were replaced by tumors 3 to 15 cm in maximum diameter; seven were bilateral. The neoplastic tissue was typically solid, but small cysts were present in two cases, and one tumor was a unilocular cyst with a solid mural nodule. On microscopic examination, tumor involved both the serosa and the parenchyma of the ovary in seven cases, the serosa only in one case, and the parenchyma only in one case. Seven tumors were exclusively epithelial, with papillary, tubular-glandular, and solid patterns, and two were biphasic. The cells in the epithelial mesotheliomas usually exhibited moderate atypicality and a low mitotic rate. The stroma was typically hyalinized, and in three of the cases with a papillary pattern papillae with hyalinized cores were a striking finding. Psammoma bodies were present in three cases. Histochemical and immunohistochemical stains confirmed the mesothelial nature of the tumor cells. Because of the wide variety of microscopic patterns in MMs, the differential diagnosis of ovarian MM includes a variety of primary and metastatic ovarian tumors as well as other peritoneal mesothelial lesions.