define focal myositis
Focal myositis is a rare condition with swelling of a single muscle, presenting usually as a painful, indolent tumour . Focal myositis may be confused with other lesions of neoplastic, vascular or inflammatory origin, and perhaps the most common misdiagnosis is a soft tissue sarcoma . Correct diagnosis is based on clinical features together with a muscle biopsy showing histological changes including necrosis and inflammatory features.