Disseminated intramuscular anaplastic plasma cell tumour in a dog

Abstract

AbstractA 12‐year‐old, neutered, male Jack Russell terrier was diagnosed with a disseminated intramuscular anaplastic round cell tumour with primary hepatic, splenic, subcutaneous and medullary involvement. The tumour was confirmed by histopathology, immunohistochemistry and polymerase chain reaction analysis of antigen receptor gene rearrangements to be of plasma cell origin. Tumour cells were lambda light chain‐positive, multiple myeloma 1‐positive and pan‐B marker‐negative (paired box protein 5, CD20 and CD79) and showed clonal immunoglobulin heavy chain gene rearrangement. Computed tomography did not identify osteolytic lesions. Plasma cells represented 14% of bone marrow cells. Serum and urine electrophoresis were not performed because of a normal serum globulin concentration. To the authors’ knowledge, this is the first case report describing a disseminated diffuse intramuscular anaplastic plasma cell tumour in a dog without evidence of multiple myeloma on initial presentation or progression to multiple myeloma or plasma cell leukaemia during follow‐up.