Fibronexus in a case of malignant fibrous histiocytoma

A 78-year-old man presented with a subcutaneous supraorbital tumor measuring approximately 4.0 x 3.0 x 1.8 cm. It was removed in several irregular portions, and histologic sections were taken from each portion. The lesion was diagnosed as a grade 3 malignant fibrous histiocytoma. Further characterization of the tumor necessitated the use of transmission electron microscopy. This appears to be the first report of fibronexus in malignant fibrous histiocytoma. This structure linked the myofibroblast with the extracellular matrix; specifically, microfilaments were linked to fibronectin fibrils. Interaction between collagen and fibronectin was noted within the extracellular matrix.