Proliferative Fasciitis and Proliferative Myositis
Proliferative fasciitis is a mass-forming subcutaneous proliferation characterized by large ganglion-like cells and plump myofibroblastic/fibroblastic cells. Proliferative myositis has the same cellular composition but occurs within skeletal muscle.
Proliferative fasciitis develops most frequently in the upper extremities, particularly the forearms, followed by the lower extremities and trunk. Proliferative myositis arises predominantly in the trunk, shoulder girdles, and upper arms and less often in the thighs. By definition, proliferative fasciitis is subcutaneous and proliferative myositis is intramuscular.
Both proliferative fasciitis and proliferative myositis characteristically grow rapidly and are usually excised within 2 months from the time they are first noted. Proliferative fasciitis almost always measures <5 cm and is most often <3 cm. Proliferative myositis may be slightly larger. Either lesion may be painful or tender; this is...