Sections show fibroadipose tissue and skeletal muscle infiltrated by a high-grade, highly cellular neoplastic proliferation arranged in solid sheets, irregular nests, and trabeculae within a prominent desmoplastic stroma. The tumor cells are undifferentiated, exhibiting marked pleomorphism, high nuclear-to-cytoplasmic ratios, and scant to moderate eosinophilic cytoplasm. Nuclei are prominently enlarged and hyperchromatic, with irregular contours and prominent nucleoli. There is brisk mitotic activity, including atypical mitotic figures, accompanied by areas of tumor necrosis. No definitive glandular formation or squamous differentiation is identified. Overall, the morphological features are those of a high-grade malignant tumor consistent with a metastatic deposit.
Thigh mass.
Soft tissue mass measured 4.8x3.5x2 cm, totally embedded.
Thigh mass, biopsy: