Tongue focal myositis: Case series and immunohistochemical characterization

Introduction: Focal myositis (FM) is an uncommon, localized inflammatory process that affects a single muscle, with unknown aetiology. In the head and neck region, involvement of perioral musculature, floor of the mouth, and sternocleidomastoid muscle have been reported. FM affecting the tongue is very rare, with only four cases previously published to date. Aim: This report describes five additional cases of tongue FM. Case Report: Three patients were male and two were female (mean age, 56 years), and three had symptomatic short-term nodular swelling. Results: By immunohistochemistry, M2 macrophages and CD4+ T cells were predominant. Focally, CD15+ granulocytes and CD20+ B cells were visualized. Polyclonal CD138+ plasma cells, with a predominance of IgG+ cells (rarely IgG4+), were detected. All patients evolved with complete resolution after biopsy and no signs of clinical or systemic progression were observed during the follow-up. Conclusions: FM should be considered in the differential diagnosis of rapidly growing nodular lingual lesions. By immunohistochemistry, a predominance of M2 macrophages and CD4+ T cells is typical, and it can help in the differential diagnosis with myositis of other origins.