Mesenteric fibromatosis: a rare cause of peritonitis

Summary

A 65-year-old Chinese man presented with a 2-day history of left-sided abdominal pain with fever and watery diarrhea in February 2016. An 11 cm x 13 cm tumour was found at the mesenteric side of the proximal jejunum which had ruptured with abscess formation. Gross examination showed a multinodular tumour with an area of purulent material on the surface at the serosa, measuring up to 11 cm in diameter. On light microscopy, a circumscribed and non-encapsulated spindle cell neoplasm was seen centred at the subserosa and muscularis propria. On immunohistochemical staining, tumour cells exhibited a beta-catenin nuclear translocation pattern and were weakly positive for c-Kit. The features were compatible with a diagnosis of mesenteric fibromatosis (MF).