Myxofibrosarcoma with an infiltrative growth pattern: A case report

Myxofibrosarcoma, also known as a myxoid variant of malignant fibrous histi ocytoma, is one of the most common sarcomas in the extremities of elderly p eople and is characterized by a high frequency of local recurrence. We repo rt a case of myxofibrosarcoma, intermediate grade, involving the thigh alon g the fascial plane and between the muscles without the formation of an app arent nodular lesion. On microscopic examination, the tumor lacked areas of necrosis and pronounced cellular pleomorphism, but it was highly cellular with proliferation of spindle cells which contained large elongated, hyperc hromatic and irregularly shaped nuclei, slightly eosinophilic cytoplasm and indistinct cell margins, arranged in both interlacing fascicles and a stor iform pattern. Immunohistochemically, many of the tumor cells showed intens e reactivity to vimentin and CD34. More than 20% of the cells were positive for p53 protein and the MIB-1 labeling index was similar to 30%. Desmin, a lpha-smooth muscle actin, muscle-specific actin, S-100 protein, cytokeratin , epithelial membrane antigen, bcl-2 protein and neurofilament were negativ e. The absence of a discrete mass lesion and diffuse infiltrative nature pr ecluded early recognition of tumor. Seven years after hindquarter amputatio n, the patient has been alive without evidence of local recurrence or dista nt metastasis. This case indicates that myxofibrosarcoma can demonstrate a highly infiltrative growth pattern. It is possible that this infiltrative n ature is associated with a high rate of local recurrence of the tumor. A ca reful radiological examination of the extension of the tumor prior to surge ry is mandatory considering the infiltrative nature of myxofibrosarcoma.