[Proliferative myositis--a little-known pseudomalignant lesion].

The leading symptom of proliferative myositis is a rapidly growing hard tumor in the muscle. The disease is rare and therefore widely unknown. We observed a case of proliferative myositis in a 54-year-old female. We initially interpreted the hard tumor in the left musculus sternocleidomastoideus and its rapid growth as a malignant disease. The histological findings finally led to the correct diagnosis. In the light of the literature of 78 reported cases, a presumptive diagnosis can already be suspected from the clinical examination. The addition of CT scan and fine needle aspiration is highly diagnostic.