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Immunohistochemical Features: Undifferentiated pleomorphic sarcomas (UPS) show no specific line of differentiation and therefore have no specific staining pattern. Immunohistochemistry is useful in eliminating other lineage-specific sarcomas.
The tumor cells have features of fibroblasts or myofibroblasts and may show patchy staining for SMA; however, they are negative for desmin, MyoD1, and h-caldesmon. Some cases have rare cytokeratin-positive cells. Weak, patchy or focal staining for any marker is not considered evidence of a specific line of differentiation. However, diffuse strong immunoreactivity for a marker is more likely to indicate the tumor lineage. For e.g. diffuse strong positivity for keratins favors sarcomatoid carcinoma and argues against the diagnosis of UPS.
The tumor cells have features of fibroblasts or myofibroblasts and may show patchy staining for SMA; however, they are negative for desmin, MyoD1, and h-caldesmon. Some cases have rare cytokeratin-positive cells. Weak, patchy or focal staining for any marker is not considered evidence of a specific line of differentiation. However, diffuse strong immunoreactivity for a marker is more likely to indicate the tumor lineage. For e.g. diffuse strong positivity for keratins favors sarcomatoid carcinoma and argues against the diagnosis of UPS.