Proliferative Myositis on the Tongue / 대한피부과학회지

Proliferative myositis is a rare, benign, probably pseudosarcomatous fibroblastic proliferation that typically presents as a rapidly growing soft tissue mass. Its relative rarity, fast growth rate, and unique histopathologic findings may lead to misdiagnosis as a malignant lesion and unnecessary radical surgical excision. A 57-year-old female presented with a non-tender, well-defined, indurated, solitary, hard papule on the median sulcus of the tongue for 2 weeks. Histologic examination revealed numerous fibroblastic or myofibroblastic spindle cells and large ganglion-like cells infiltrating between and around the muscle fascicles. Immunohistochemical staining showed positivity for vimentin, smooth muscle actin, and CD68 and negativity for S-100. Based on these characteristic clinical findings and histopathologic features, the patient was diagnosed with proliferative myositis. Here, we report a rare case of proliferative myositis on the tongue and recommend considering proliferative myositis in the differential diagnosis when a physician encounters a rapidly grown soft tissue mass.

A Case Report of Proliferative Myositis in Pectoralis Major Muscle

Proliferative myositis is very rare and was first described as a specific entity in 1960 by Kern. Proliferative myositis is a benign reactive condition that appears as a rapidly growing mass in the proximal muscles of the extremities of adults. Proliferative myositis can be confused with sarcoma clinically as well as microscopically. Proliferative myositis is a bizarre, self-limiting fibroblastic proliferation, the presence of very large basophilic cells with vesicular nucleoli and very prominent nucleoli which resemble ganglion cells or rhabdomyoblast, the cause of which is unclear. The symptoms are non-specific and the diagnosis always rests on a histological examination of the tissue. Local excision is curative and recurrence or metastasis has not been reported even when the abnormal tissue has not been completely excised. The authors report a case of Proliferative myositis in a 59-year-old male.