In myofibroblastic sarcomas of the head and neck, mitotic activity and necrosis define grade: a case study and literature review.

Low-grade myofibroblastic sarcoma (LGMFS) is considered a distinct entity in the World Health Organization classification of soft tissue neoplasms, defined as an atypical myofibroblastic proliferation with fibromatosis-like features and a predilection for the head and neck. A substantial subset of previously reported myofibroblastic sarcomas (MFS), particularly in the head and neck region, are associated with appreciable tumor-associated morbidity and mortality and should be differentiated from the more indolent LGMFS. However, no specific morphological criteria have been developed to define the entity of LGMFS. We have reviewed histological findings in conjunction with clinical follow-up information of previously reported MFS in the head and neck region in the English literature, with the addition of five new cases from our institution. We found that MFSs with 6 or more mitoses per 10 high power fields and/or presence of spontaneous necrosis were accompanied by a higher mortality rate that is statistically significant.