Focal myositis of esophagus: a distinct inflammatory pseudotumor mimicking esophageal malignancy

Focal myositis is a benign pseudotumor of skeletal muscle that usually occurs in the soft tissue of the extremities. Clinically, it grows rapidly but usually regresses spontaneously and is often misdiagnosed as a malignancy. We report a case of focal myositis occurring in the upper esophagus and presenting as a rapidly growing submucosal tumor with severe esophageal stenosis and dysphagia. It was misdiagnosed preoperatively as esophageal malignancy. Histologically, it was characterized by the presence of various-sized skeletal muscle fibers with interstitial inflammation and fibrosis. The pathological pictures are identical to polymyositis or dermatomyositis, but the stenosis was relieved after operation without recurrence, and levels of the polymyositis-associated autoantibodies and serum enzymes were not elevated. Therefore, clinical and histological information is needed to make a correct diagnosis.