Myofibrosarcoma of the upper jawbones: A clinicopathologic and ultrastructural study of two cases

Two problematic spindle cell sarcomas involving upper jawbones in two adult male patients have been studied by histology, immunohistochemistry, and tr ansmission electron microscopy, and respectively graded as low-grade malign ancy and high-grade malignancy. While any single methodological study did n ot allow confident classification of them into one or other of the classica l categories of spindle cell sarcomas (fibrosarcoma versus leiomyosarcoma), the overall contribution from all three methodologies ultimately allowed t hem to be categorized as sarcomas with myofibroblastic differentiation. His tologically, both tumors had morphological features of an amalgama between neoplastic fibroblasts and smooth muscle cells. Immunohistochemically, both tumors expressed reactivity only for muscle specific actin and alpha smoot h muscle actin, in addition to vimentin. Ultrastructurally, both tumors, wh ile showing fibroblast-like cytoplasmic features, had a spurious and imperf ectly organized cell surface defying convincing classification into any of specific categories (i.e., both appeared in terms of ultrastructure as poor ly differentiated sarcoma, the former with low level of smooth muscle diffe rentiation and possibly the presence of some fibronexus component, the latt er with no smooth muscle differentiation but with possible evidence of very rare fibronectin fibril). Therefore, on balance, the most tenable diagnosi s seemed to us that of a myofibrosarcoma in both cases. This work is presen ted considering the fact that myofibrosarcoma currently represents a topica l theme of debate, and that this is the first report in medical literature concerning with myofibrosarcomas of the head and neck area in adults.