Myxofibrosarcoma

Myxofibrosarcoma is a fibroblastic sarcoma of late adult life, usually presenting as a painless superficial or subcutaneous mass in the limbs, and is now the commonest sarcoma diagnosis in the elderly. Its defining behaviour is infiltrative growth along fascial planes and septa well beyond the palpable mass, seen on MRI as curvilinear tail-like enhancement, and this explains a local recurrence rate that exceeds every other soft tissue sarcoma. Grade rises with each recurrence, and metastasis, mainly to the lungs, follows grade: rare in low-grade tumours, common in high-grade ones.

Treatment is wide surgical resection planned on contrast-enhanced MRI to encompass the tail sign, with radiotherapy for most intermediate- and high-grade tumours and for recurrent disease, given preoperatively or postoperatively as for other extremity sarcomas. Positive margins are common even in expert hands and re-excision is frequently needed. Systemic therapy for high-grade or metastatic disease follows the general soft tissue sarcoma approach with doxorubicin-based chemotherapy, and the tumour has no recurrent driver alteration to target.

Research has focused on the genomics of progression, with recurrent copy number gains and losses and TP53, CDKN2A and RB1 alterations shared with undifferentiated pleomorphic sarcoma, and on defining surgical margins by imaging so that the first operation is the last.