Bilateral Well-Differentiated Papillary Mesothelioma of the Ovaries—a Diagnostic and Therapeutic Enigma

Introduction

Well-differentiated papillary mesothelioma (WDPM), an uncommon variant of epithelial mesothelioma, has been reported to occur in the peritoneum, pericardium, tunica vaginalis, and ovary. At times, it is detected incidentally at laparotomy done for other indications.^1,2 A WDPM arising from the ovary may be difficult to differentiate from its malignant counterpart (malignant mesothelioma), which is also a rare tumor, and from the more common ovarian adenocarcinoma. This differentiation is imperative due to wide variations in clinical behavior, the need for adjuvant therapy, and the prognosis of these tumors.

Only three cases of WDPM of the ovary have been documented in the literature to date, all of which were unilateral and <6 cm in size.^1,3 We report here a case of bilateral large papillary mesothelial ovarian tumors measuring 15 cm and 8 cm and showing low-grade histological features observed in WDPM.

Case

A 48-year-old menopausal, para 4 woman was admitted with complaints of dull pain in her lower abdomen for the previous 3 months. She had not noticed any loss of weight or appetite. On general physical examination, she was pale, anicteric, and of moderate built. Abdominal examination did not reveal any lump or hepatosplenomegaly. However, ascites was detectable. Bimanual pelvic examination demonstrated a normal-sized anteverted uterus and bilateral, irregular, firm, and nontender adnexal masses of 10–15 cm in size. She had a hemoglobin of 7 gm% and CA-125 of 209 U/mL. Ultrasonography revealed irregular hypoechoic masses involving both adnexae but separate from the uterus, with foci of calcification and flow on Color Doppler. Free fluid was detectable in the abdomen, the liver was normal in appearance, and there was no paraaortic lymphadenopathy. After a complete preoperative work-up, the patient was taken up for laparotomy.

Two liters of hemorrhagic fluid was aspirated at laparotomy. Both adnexae were engulfed by pinkish, soft, irregular papillary tumors, measuring 15×15 cm on the left side and 8×8 cm on the right side (Fig. 1). Without sectioning, little greyish white ovarian tissue could be identified on the left side. The uterus and other pelvic organs as well as the liver, omentum, and gut appeared normal. With a working diagnosis of malignancy of the ovaries, a total hysterectomy with bilateral salpingo-oophorectomy, infracolic omentectomy, and peritoneal sampling was carried out. The patient fared well postoperatively.

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FIG. 1.

Intraoperative picture showing the uterus and papillary tumors enveloping both ovaries.

Histopathology of the peritoneal biopsies and omental tissue were negative for infiltration by the tumor. Ascitic fluid was negative for malignant cells and was reported as reactionary effusion. The uterus and cervix were unremarkable. Both ovaries were enveloped by papillary fronds of variable size, measuring from 2 to 10 mm, together aggregating to 15 cm on the left side and 8 cm on the right side.

Microscopic examination of the tumor showed variable-sized papillary structures, all lined by single layer of epithelium-like cells without ciliary processes and mucin secretions. The core showed mature connective tissue with few thin-walled blood vessels (Fig. 2).

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FIG. 2.

Papillary mesothelial tumor arising from the surface of the ovary. Fibrovascular papillary structures are lined by single-layered cuboidal to columnar epithelium without stratification. Ovarian stroma identified toward the right lacks invasion (100×H&E stain).

The structure of fallopian tube could be identified on both sides. Ovarian tissue inclusive of the corpus albicans was also identifiable, enveloped by papillary projections on the surface.

Discussion

Mesotheliomas arising from the peritoneum are often considered highly aggressive, multifocal tumors and are usually associated with a history of exposure to asbestos. However, its rare variant—WDPM—is usually benign and predominantly affects the peritoneum of women who have no history of exposure to asbestos. ³

Correct diagnosis of the lesion is important because of therapeutic and prognostic considerations. The close differential diagnosis includes papillary serous adenocarcinoma of the ovary and metastatic deposits of papillary tumors elsewhere in the abdomen (gastrointestinal tract, hepatobiliary, etc.). ³

The largest series of WDPM pertains to 22 cases arising from different sites (two were ovarian), of whom 18 were women and showed multifocal lesions. ¹ Postoperative adjuvant chemotherapy or radiotherapy was administered in 60% these cases. Five women died of unrelated causes, whereas four cases showed local recurrence of variable sizes or persistence ascites. Since all the ovarian cases (except one, which was 6 cm in size) reported so far have been <2 cm and unilateral, excision of the tumor has been considered adequate.^1,3

Our case is different from these sparingly reported ovarian neoplasias in respect of showing bilaterility, ascites, and the large tumor size. Extensive sampling of the tumor for histopathology did not reveal cytoarchitecture of high-grade histology like stratification, nuclear anaplasia, significant mitotic activity, and stromal invasion (Fig. 2).

The tumor was differentiated from other surface epithelial ovarian tumors like papillary serous cystadenocarcinoma, since grossly both the ovaries were enveloped by papillary fronds of the tumor without involvement of ovarian tissue. On microscopy, the fibrovascular core of papillary structures lined by single layer of cuboidal to columnar cells with absence of mucin and low nuclear cytoplasmic ratio precluded the possibility of other ovarian tumors. ¹ Although the tumor was bulky, absence of mitosis, desmoplasia, and necro-inflammatory reaction associated with tumor invasion differentiated this lesion from malignant mesothelioma and ovarian carcinoma. ⁴

This patient was treated in the same way as for ovarian carcinoma, including drainage of ascitic fluid, and peritoneal and omental sampling, apart from panhysterectomy. The tumor was restricted around both of the ovaries only, the peritoneum, omentum, and ascitic fluid being negative for tumor cells. Since multifocality has been described in many cases of WDPM of the peritoneum, we are planning adjuvant therapy to prevent recurrence, keeping in view the large size and bilaterility, even though extensive sampling did not reveal microscopic features of malignancy. ¹