Sclerosing rhabdomyosarcoma presenting on the knee-joint.

Sclerosing rhabdomyosarcoma is a rare pathological diagnosis that easily misdiagnosed. The majority of cases reported the tumor increased rapidly in size and the Ki-67 proliferation index ranged from 10% to 60%. Here, we report the fi rst case of the tumor increased very slowly for 20 years and the Ki-67 proliferation index was lower than 2%, and discuss its histological features and immunohistochemical reactivity with Desmin and Ki-67 and so on.