Retroperitoneal nodular fasciitis: a benign etiology on the differential diagnosis of malignant gastric outlet obstruction

Nodular fasciitis is a relatively rare, benign and proliferative lesion that is not typically found in the retroperitoneal (RP) space and has not been previously reported as a cause of gastric outlet obstruction (GOO). GOOs are frequently associated with malignancies, however, benign etiologies should be considered as well. We report the first case of GOO secondary to nodular fasciitis in the form of a spontaneously regressing RP mass that was initially concerning for malignancy.