A 48-year-old man presented with a 3-month history of weight loss and progressive right lower quadrant abdominal pain. His medical history was notable for appendectomy at age 17. Ultrasonography and computed tomography of the abdomen revealed a 12 cm multicystic mass in the right paracolic space. At laparotomy a large serous cyst was found arising from the lateral wall of the cecum, and four additional small cysts were found on the small bowel mesentery, greater omentum, liver capsule, and right hemi-diaphragm. Complete removal of the tumor was accomplished by right colectomy with extraperitoneal dissection of the large cyst and simple excision of the four smaller cysts. Final pathology with immunohistochemical staining confirmed cystic mesothelioma of the peritoneum. In this report we discuss the diagnostic workup and treatment of this rare disease.
