Tumoral calcinosis is a rare form of soft tissue calcifications, initially described as an idiopathic condition, which could occur in uremic patients. Despite its distinct clinical and morphologic presentations, the underlying pathogenesis is unknown. We present a dialysis patient who developed tumoral calcinosis over the right shoulder after receiving a misplaced injection of human recombinant erythropoietin probably into the periarticular tissue. This case serves as an example highlighting the importance of periarticular inflammatory reaction in precipitating the development of the lesion in predisposed patients. © 2002 by the National Kidney Foundation, Inc.