Proliferative myositis (PM) is a rare, benign, neoplastic condition of the skeletal muscle. To date, approximately 100 cases have been published in which 25 reported lesions were located in the head and neck region. In spite of its rarity, PM is an important differential diagnosis for the ear, nose, and throat surgeon because it clinically resembles a malignant tumor. Typical findings that should raise suspicion include a rapidly, invasive growing tumor within skeletal muscle and absence of enlarged lymph nodes, in conjunction with an unremarkable laboratory workup. Ultrasonography of the tumor can give an important hint toward the correct diagnosis. However, a biopsy is mandatory, and the diagnosis is made by the pathologist. It is justifiable to wait and monitor the lesion, since PM is a self-limiting proliferation and spontaneous recoveries have been described. Malignant transformation or metastases have not been reported.
Fauser C, Nährig J, Niedermeyer HP, Arnold W. Proliferative MyositisA Rare Pseudomalignant Tumor of the Head and Neck. Arch Otolaryngol Head Neck Surg. 2008;134(4):437-440. doi:10.1001/archotol.134.4.437