[Anatomic-clinical confrontation. Large pelvic mass in a young man]

The authors report the case of a gastro-intestinal stromal tumor (GIST) with unusual clinico-pathological features, presenting as a large cystic rectal mass in a young man. The differential diagnosis of pelvic masses is discussed. In light of this case, the recent literature related to the pathogenesis, diagnosis and treatment of GIST is reviewed.