Myofibrosarcoma of subcutaneous soft tissue of the cheek
Eyden, B.P.; Christensen, L.; Tagore, V.; Harris, M.
Journal of Submicroscopic Cytology and Pathology 24(3): 307-313
1992
ISSN/ISBN: 1122-9497 PMID: 1394086 Document Number: 396199
A low grade soft tissue sarcoma from the naso-labial fold and designated as myofibrosarcoma (sarcoma of myofibroblasts) is described using standard light microscopy techniques, immunohistochemistry and electron microscopy. Pink fibrillated cytoplasm, regarded as one of the typical histological features of leiomyosarcoma, was not obvious but immunostaining for .alpha.-smooth muscle actin was positive suggesting smooth muscle differentiation. By electron microscopy, tumour cells contained abundant rough endoplasmic reticulum cisternae and a large Golgi body; there were modest but numerous bundles of fine filaments with focal densities. A conventional lamina was lacking but the cell surface was characterised by fibronexus junctions in which there was a conspicuous extracellular, fibronectin-containing fibril, apparently mediating contact between cell and matrix. The tumour cells therefore showed myofibroblastic differentiation. The cell surfaces showed strong immunoreactivity with anti-fibronectin antibody. Myofibrosarcoma is not a widely recognised entity and this case is only the 7th example to be documented in detail by means of both immunohistochemistry and ultrastructure. The combination of electron microscopy for detecting the fibronexous junction and immunostaining for fibronectin at the cell periphery is suggested as potentially useful for distinguishing myofibrosarcoma from leiomyosarcoma.