Extraperitoneal parastomal metastasis of malignant peritoneal mesothelioma.

A 75-year-old man was referred to surgical outpatient department with what was thought to be a parastomal hernia. Through further investigations with CT and biopsy, it was identified that the parastomal mass was metastatic peritoneal mesothelioma in the abdominal wall and subcutaneous tissue. The patient had a significant surgical history including a previous abdominoperineal resection with end colostomy 9 years prior and a right hemicolectomy for small bowel obstruction the previous year which diagnosed peritoneal mesothelioma. Peritoneal mesothelioma often spreads throughout the abdominal cavity and rarely spreads outside the peritoneum, with this being the first case describing parastomal metastasis. Given the patient's surgical background, this is possible to have contributed to seeding the spread of peritoneal mesothelioma.