Necrotizing arteritis causing fatal massive intraperitoneal hemorrhage from a pancreatic pseudocyst.

We report the histopathological findings from a medicolegal autopsy case caused by sudden massive hemorrhage from a necrotic pancreatic cyst into the abdominal cavity. The histological examination revealed that the wall of the cyst was filled with hematoma and consisted of granuloma at a relative early stage, involving marginating lymphocytes, foamy lipophages, cholesterin crystals, foreign body giant cells with neutrophiles, mast cells and fibrous tissues. Since there was no epithelial lining, the lesion was diagnosed as a pseudocyst. In the wall of this pseudocyst, small arteries showed acute intense necrotizing inflammatory reactions in association with fresh thrombi. Trace of elastic fibers remained in the wall of the arteries. Since the small veins in the wall showed varix-like changes without necrosis or inflammation, it is proposed that the lethal bleeding was caused by rupture of the small arteries that exhibited severe arteritis.