[Colon carcinoma simulating retroperitoneal inflammatory pseudotumor. Case report of so-called abdominal inflammatory fibrosarcoma].

Resection of a stenosing colon tumor in an 89-year-old male patient led to the diagnosis, unusual at this age, of an inflammatory pseudotumor (synonym: plasma cell granuloma) of the retroperitoneum and mesentery, which invaded the large bowel and showed infiltration of one regional lymph node. Histology and immunohistochemistry (demonstrating a myofibroblastic phenotype of the proliferating spindle cells and polyclonality of abundantly present plasma cells) of the specimen resembled previously reported lesions in various locations. The etiology and exact nosological classification of inflammatory pseudotumors are not yet unequivocally settled. The recently published conjecture that such lesions of the retroperitoneum represent a separate entity with features of a malignant neoplasm is discussed.