Sections demonstrate a lymph node with the architecture distorted by a prominent nodular infiltrate. The infiltrate is composed of undifferentiated, pleomorphic, anaplastic cells with vacuolated nuclei showing an open chromatin pattern, focal prominent nucleoli and a moderate amount of cytoplasm. There are abundant mitotic figures, some rather bizarre. In some areas, residual lymph node architecture is maintained. Cytokeratin stain is focally positive in the tumor cells. Leukocyte common antigen (LCA) is negative.