Low-grade myofibroblastic sarcoma of the tongue

Low-grade myofibroblastic sarcoma is a neoplasm of atypical myofibroblasts with fibromatoseslike features and a predilection for head and neck sites, including the oral cavity. These lesions have only been characterized in the last 2 decades, and controversies in the concept of neoplastic myofibroblasts still exist. Lack of obvious cytological atypia may result in their being mistaken for reactive fascitislike lesions or fibromatosis and architectural similarities to fibrosarcoma or leiomyosarcoma may complicate the diagnostic process. This paper describes a spindle cell neoplasm in a 40-year-old man that was diagnosed 9 years ago as an unclassifiable myofibroblastic proliferation. The recurrent tumor, which presented 6 years following excision of the original tumor, was subsequently classified as a low-grade myofibroblastic sarcoma. The morphological, immunohistochemical, and electron microscopic features of this unusual sarcoma and the most likely differential diagnoses are discussed.