Malignant peritoneal mesothelioma presenting as a mass in a Spigelian hernia. Report of a case

BACKGROUND: Gastrointestinal cancer, gynecologic cancer and malignant peritoneal mesothelioma may disseminate widely to the surfaces of the abdomen and pelvis. In some patients this spread of the disease may find its way into a hernia sac. METHODS: The Spigelian hernia is caused by a protrusion of the peritoneum of the anterior abdominal wall into the abdominal wall muscle. This peritoneal defect occurs through the semilunar line of Spiegel in or closely associated with the semicircular line of Douglas. RESULTS: A patient presented with a large (11 cm greatest diameter) mass in the left lower quadrant. The mass was composed of malignant peritoneal mesothelioma and was anatomically located within the Spigelian hernia belt. At the time of cytoreductive surgery numerous other sites of malignant peritoneal mesothelioma were present within the abdomen and pelvis. CONCLUSIONS: The left lower quadrant mass was a malignant peritoneal mesothelioma presenting within a Spigelian hernia defect. This phenomenon has not been previously reported.