Case description: A 9-year-old castrated male mixed-breed dog and a 7-year-old spayed female Boston Terrier, with clinical histories of a liver mass (dog 1) and bloody vomitus, diarrhea, and weight loss (dog 2), respectively, were referred for further evaluation.
Clinical findings: At the time of referral, each dog had differing laboratory abnormalities; however, the serum total protein and globulin concentrations were within reference range in both dogs. Cytologic examination of fine-needle aspirates obtained from affected organs (a liver mass [dog 1] and enlarged submandibular lymph node [dog 2]) revealed 2 main nucleated cell types: atypical lymphoid cells and lesser numbers of Mott cells. With the use of serum immunofixation electrophoresis and serum immunoglobulin quantification, a monoclonal immunoglobulin protein was identified in both dogs and a final diagnosis of secretory B-cell lymphoma with Mott cell differentiation (MCL) was made.
Treatment and outcome: Both dogs received chemotherapy for their disease. The first dog was euthanized 8.5 months after diagnosis because of acute respiratory distress of unknown etiology, and the second was euthanized 7 days after diagnosis for worsening clinical disease and quality of life.
Clinical relevance: To our knowledge, this report is the first of a secretory form of MCL in dogs. Findings indicate that in dogs with suspect MCL, even in patients that lack characteristic hyperproteinemia or hyperglobulinemia, serum protein content should be fully evaluated for the presence of a monoclonal immunoglobulin protein. Such an evaluation that uses immunofixation electrophoresis and immunoglobulin quantification will aid in the diagnosis of MCL in dogs.