Retroperitoneal calcifying fibrous tumor mimicking an adrenal tumor.

Establishing the etiology of a retroperitoneal tumor may be difficult due to close proximity of multiple organs. Evaluation of retroperitoneal tumors often leads to surgery, many times to obtain a definitive diagnosis and rule out malignancy. Calcifying fibrous tumors (CFT) are very rare soft tissue tumors occurring most often in young patients. They are most often found arising in the thoracic cavity, mediastinum, abdominal cavity and extremities and usually have a benign clinical course. Macrocscopically, the tumors are well circumscribed and firm with a white-tan appearance. Histologically, CFT comprised a hypocellular proliferation of bland spindle cells, densely hyalinized collagen, chronic lymphoplasmacytic inflammation and dystrophic calcifications. Other considerations in the pathologic differential diagnosis include solitary fibrous tumor and inflammatory myofibroblastic tumor.