MUM1 expression in lymphomas and myeloma.

(A) Diffuse, large B-cell lymphoma showing nuclear and cytoplasmic positivity for the MUM1 protein. Arrowheads point to large MUM1⁺ tumor cells with prominent nucleoli (lymph node paraffin section; × 800). (B) Diffuse, large B-cell lymphoma showing no expression of the MUM1 protein. The arrow points to a normal residual MUM1⁺ cell (lymph node paraffin section; × 1000). (C) Multiple myeloma showing strong nuclear and cytoplasmic positivity of tumor cells for the MUM1 protein (paraffin section from bone marrow trephine biopsy; × 250). (D) Strong nuclear and weak cytoplasmic expression of the MUM1 protein in a Reed–Sternberg cell of Hodgkin's disease, nodular sclerosing type (lymph node paraffin section; × 1000). (A-D) Immunostaining with the MUM1p monoclonal antibody; APAAP procedure; hematoxylin counterstain.