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The patient was taken to the operating room for an explorative laparoscopy. A 6-cm–diameter pedunculated mass of the greater curvature/anterior wall of the stomach was identified. The mass was removed through a small laparotomy incision (Figure 2); the patient experienced an uneventful recovery and was discharged on the third postoperative day. The gross pathology revealed a gray-brown encapsulated mass. Histopathologic examination revealed a partially cystic, highly vascular, well-encapsuled neoplasm. Immunohistochemistry showed positive staining of tumor cells for cytokeratin and calretinin. A follow-up computed tomographic scan of the abdomen revealed no recurrence at 9 months postoperatively.

Benign multicystic peritoneal mesothelioma is an extremely rare neoplasm originating from the visceral and parietal peritoneum of the abdominal cavity. Fewer than 150 cases have been reported in the literature so far.¹ It was first described back in the late 1920s by Plaut,² but the mesothelial origin of this disease was unknown until 1979.³ Several names have been used to describe this condition, including multicystic peritoneal proliferation, multilocular peritoneal inclusion cyst, postoperative peritoneal cyst, adenomatoid tumor, and cystadenoma.^4- 5 The pathogenesis of this benign lesion is not clear. Several authors, on the basis of its progressive growth and potential for recurrence, believe that there is a neoplastic etiology. Others, based on both the virtual lack of risk of metastases for this lesion and the recent reports of cases in patients with previous abdominal surgery or infection, have suggested that this lesion is simply a reactive proliferation of mesothelial cells.

Benign multicystic peritoneal mesothelioma usually occurs in middle-aged women with a history of abdominal surgery. Clinical features at presentation are nonspecific and include nausea, vomiting, abdominal pain, constipation, and a palpable mass. Ultrasound, computed tomography, and magnetic resonance imaging often do not allow differentiation from other cystic or noncystic lesions.⁶ The use of fine-needle biopsy is unlikely to provide further information because the aspirate usually shows reactive, aspecific mesothelial cells. During surgery, benign multicystic peritoneal mesothelioma appears as a multicystic tumor with translucent cysts filled with gelatinous fluid and separated by fibrous septa. On histopathologic examination, cysts are lined with single or multiple layers of cuboidal cells that are immunoreactive for epithelial antigens.⁷ Nonoperative management with close follow-up in asymptomatic patients with benign multicystic peritoneal mesothelioma is considered a valid alternative to surgical resection, although, given the difficulties in the preoperative diagnosis, the usual practice is surgical exploration with total excision for localized lesions. Laparoscopic treatment has also been described in the literature.⁸ Despite a recurrence rate ranging between 25% and 50%, the benign characteristics of benign multicystic peritoneal mesothelioma make adjuvant chemoradiotherapy and heated intraoperative intraperitoneal chemotherapy of no use—although both are still recommended in some reports.^9- 10 All authors do agree, however, that close postoperative follow-up with ultrasound or computed tomographic scans is recommended.

Giuseppe Portale, MD, Department of Medical and Surgical Sciences, Clinica Chirurgica III, University of Padova School of Medicine, Via Giustiniani 2, Padova, Italy (portale@surgery.usc.edu).

March 10, 2006.

: Portale, Costantini, and Zaninotto. : Portale, Guirroli, Costantini, and Rampado. : Portale, Costantini, Zaninotto, and Ancona. : Guirroli and Rampado. : Portale, Costantini, Zaninotto, and Ancona. : Guirroli and Rampado. : Portale, Costantini, and Ancona.

None reported.