This breast lesion
shows sheets of dyscohesive anaplastic cells with broad
pale-eosinophilic cytoplasm. The tumor cells are negative for
cytokeratin, T-cell/B-cell markers and S100.
Neoplastic plasma cells
may show a variety of morphologic features, which may not look
like plasma cells at all. In some cases, scattered tumors cells
with typical plasma cell morphology may be present with careful
observation at high-power. Touch-imprint and smear may be very
helpful since tumor cells may show better plasma cell features in
differentiated tumors, it is probably worthwhile to keep several
differential diagnoses in mind: poorly differentiated carcinoma,
melanoma, rhabdomyosarcoma, anaplastic large cell lymphoma - null
cell type, plasmablastic/anaplastic plasma cell neoplasm, and
plasmablastic/anaplastic/immunoblastic B-cell lymphoma.