Undiff. Pleomorphic Sarcoma: Immunohistochemistry

Comments:
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.