myofibrosarcoma

The concept of soft tissue sarcomas composed predominantly of myofibroblasts has been controversial.

Myofibrosarcomas are indolent low-grade or occasionally aggressive intermediate-grade sarcomas which can be recognized by light microscopy.

Their clinical importance lies in the resemblance, particularly of low-grade examples, to reactive or pseudosarcomatous conditions.

Synopsis

 men > women
 33 to 73 years (median, 54 yrs; mean, 53 yrs)
 Lesions mainly involved the head and neck, extremities, and trunk and ranged in size from 1.5 to 12 cm.
 The tumors are composed of bland or pleomorphic stellate to spindled cells with eosinophilic cytoplasm and tapered nuclei in a collagenous stroma; 10 were grade 1 and five were grade 2.
 All myofibrosarcomas display fascicular or storiform patterns.
 Some of the grade 1 lesions superficially mimick nodular fasciitis.
 Electron microscopy show myofibroblastic differentiation.

Immunohistochemistry

 smooth muscle actin (13/15 cases)
 muscle-specific actin (7/9)
 desmin (6/14)
 cytokeratin (0/11/

References

 Montgomery E, Goldblum JR, Fisher C. Myofibrosarcoma: a clinicopathologic study. Am J Surg Pathol. 2001 Feb;25(2):219-28. PMID: 11176071