Multiple myeloma in dogs: Use of the cell block technique as a new diagnostic tool.

Abstract

The diagnosis of multiple myeloma (MM) in dogs may be challenging and complex. The cell blocks are a diagnostic technique that allows the characterization of neoplastic cells and, therefore, might help in the diagnosis of atypical MM. The objective of the present work is to describe three clinical cases in which the cell blocks and immunohistochemistry contributed to the definitive diagnosis of canine MM. Three dogs, one female and two males, with different clinical signs, were presented for consultation with anemia, hyperproteinemia with monoclonal gammopathy, and the presence of plasmacytosis in the bone marrow. Cytologic analysis of the spleen was performed in two dogs and was suggestive of the presence of lymphocytes or plasma cells of a neoplastic nature in one of the cases and plasma cell hyperplasia associated with extramedullary hematopoiesis in the other. Given the hypotheses of lymphoid neoplasms with a plasma cell phenotype, cell blocks from aspiration punctures were performed for immunohistochemical analysis with anti-CD3, CD20, CD79αcy, PAX5, and MUM1 antibodies. The results revealed positive staining for MUM1 in 80% of the cells in the spleen cell block and for CD20 and MUM1 in 70% of the cells in the bone marrow cell blocks, with negative staining for the other antibodies. The immunophenotyping results allowed the diagnosis of MM in the three cases and excluded other lymphoid neoplasms. This work reinforces the importance of using cell blocks in the diagnosis of neoplasms by demonstrating their potential to aid the diagnosis of MM.