Notes: Tumors may secondarily involve the peritoneum by direct spread from the abdominal viscera or by metastatic seeding from distant sites. The primary tumors are most often located in the ovaries, uterus, large bowel, or pancreas. The ovarian and uterine primaries are usually of serous type. The metastatic deposits may form discrete tumor nodules or cause diffuse thickening of the peritoneum. Peritoneal carcinomatosis often results in recurrent ascites and has overlapping morphologic features with malignant mesothelioma.