MICROSCOPIC DESCRIPTION:
Paraffin sections show fragments of a densely hypercellular tumour. Tumour cells have plasmacytoid features with round and oval vesicular nuclei with a clock face arrangement of chromatin. Many have conspicuous nucleoli. There is a moderate amount of basophilic cytoplasm. Frequent mitotic figures are identified. Involvement of marrow spaces of bone is seen in specimen 3. Immunohistochemistry shows strong staining for CD138 and CD79a. There is also lambda light chain restriction. The features are of plasmacytoma/myeloma.
FINAL DIAGNOSIS: Plasmacytoma/myeloma