Extensive myxoid change in well-differentiated papillary mesothelioma of the pelvic peritoneum

We present a unique case of papillary mesothelioma of the pelvic peritoneum with extensive myxoid change in a 44-year-old woman. The patient presented with lower abdominal pain; imaging studies revealed a pelvic mass. Microscopic examination of the surgically resected specimen showed extensive areas of myxoid stroma and only focal areas of classical papillary mesothelioma. A small biopsy of this lesion might have been misinterpreted as a soft tissue neoplasm with myxoid stroma or pseudomyxoma peritonei. It is suggested that mesothelioma with myxoid change should be included with differential diagnoses of myxoid lesions of the peritoneum.