Focal myositis of the floor of mouth: report of two cases and review of the literature.

Focal myositis is an uncommon inflammatory myopathy of unknown cause affecting skeletal muscle. It may be mistaken on clinical evaluation for a malignant neoplasm. We describe two cases, both involving the mylohyoid muscle of the floor of the mouth. In each case excisional biopsy of a firm indurated mass revealed a focal lymphocytic and histiocytic infiltrate associated with degenerating and regenerating skeletal muscle fibers. No clinical or biochemical evidence of generalized muscle disease was seen at presentation or at 1-year and 7-year follow-up examination. The literature on focal myositis involving the head and neck region is reviewed.