Hepatosplenic lymphoma and visceral mast cell tumor in the liver of a dog with synchronous and multiple primary tumors

An 11-year-old spayed female American Cocker Spaniel was presented with a 4-week history of anorexia and a 1-week history of abdominal distension. Clinicopathologic and imaging abnormalities included intra-abdominal hemorrhage, granular lymphocytes (GLs) in abdominal fluid smears, a splenic mass, and hepatomegaly with diffuse multiple hypoechogenic nodules. Based on the cytologic, histologic, and immunohistochemical evaluation of the spleen and liver, the diagnosis was hepatosplenic T-cell lymphoma (HSTCL) of GLs. Postoperatively, the dog was maintained in good condition with chemotherapy (ACNU [nimustine], L-asparaginase, and prednisolone). However, on day 85, ultrasound-guided fine-needle aspiration of the liver revealed a proliferation in neoplastic mast cells not associated with the GLs. The dog was diagnosed with a visceral mast cell tumor (MCT) originating from the liver. The chemotherapy was switched to vinblastine and toceranib. The dog remained in good condition until day 141 but died due to the progression of MCT on day 158. Liver cytology on day 155 showed no GLs, although HSTCL is thought to be resistant to chemotherapy. After the definitive diagnosis of HSTCL, we monitored this patient's response to chemotherapy with blood tests, including complete blood counts, ultrasound imaging, and cytologic aspirates of liver. Although canine HSTCL has a poor prognosis, the possibility of a new neoplasm, including visceral MCT, should be considered. Periodic liver cytology might be worthwhile in dogs receiving chemotherapy for HSTCL.

Lymphocytosis and lymphadenopathy in a dog arising from two distinct lymphoid neoplasms

A 10-year-old intact male Golden Retriever was presented to The Ohio State University Veterinary Medical Center for acute, non-painful facial swelling of the right mandibular region. On physical examination, the right mandibular swelling was found to represent marked lymphadenopathy of the submandibular lymph node. At this time, marked lymphadenopathy of the prescapular and popliteal lymph nodes was also appreciated. The CBC showed a moderate leukocytosis (38.4 × 10⁹ cells/L, reference interval [RI] 4.8-13.9 × 10⁹ cells/L) characterized by a moderate lymphocytosis (28.4 × 10⁹ cells/L, RI 1.0-4.6 × 10⁹ cells/L). Evaluation of peripheral blood and enlarged prescapular and popliteal lymph nodes revealed two morphologically different populations of homogeneous lymphocytes, with the lymphocyte population in the lymph nodes being distinct from that in the blood smear. Flow cytometry of peripheral blood revealed CD45-, CD5+, CD4-, CD8-, variably CD21+ neoplastic lymphocytes compatible with T-zone lymphocytes due to the absence of CD45 expression. Flow cytometry of the lymph node aspirate indicated a distinct population of CD21+ lymphocytes consistent with a B-cell phenotype along with a smaller proportion of the T-zone lymphocytes observed in the blood confirming the presence of two distinct populations of neoplastic lymphocytes, one involving T cells, and the other involving B cells.

A case of T-cell chronic lymphocytic leukemia progressing to Richter syndrome with central nervous system involvement in a dog

An 8-year-old neutered Beagle dog was presented with polyuria and polydipsia. Routine clinicopathologic testing showed a significant lymphocytosis and proteinuria. Lymphocytes were of small to intermediate in size with a mature morphology. Infectious disease screening was negative. PCR for antigen receptor gene rearrangements showed a clonal T-cell receptor (TCR) rearrangement consistent with T-cell chronic lymphocytic leukemia (CLL). Bone marrow cytology showed <30% lymphocytes, while the proportion in splenic fine-needle aspirate cytology was considered increased. The dog was initially monitored but started on prednisolone and chlorambucil therapy 2 months later due to worsening clinical signs and progressive lymphocytosis. After an additional 2 weeks, the dog developed multifocal spinal pain and single-node lymphadenomegaly. Cytology of the lymph node showed a monomorphic population of large lymphoblasts consistent with lymphoma. Cytology of a cerebrospinal fluid sample also showed large lymphoblasts. PCR for antigen receptor gene rearrangement at both sites showed a clonal TCR rearrangement of the same molecular size as in the initial leukemic cells. The dog was diagnosed with a transformation of the CLL to Richter syndrome (RS) with involvement of the central nervous system (CNS). Therapy was started with L-asparaginase and an increased dose of prednisolone; however, the dog was euthanized due to progressive clinical signs. To our knowledge, this is the first report of canine RS with direct involvement of the CNS.

Chronic lymphocytic leukemia transformation into high-grade lymphoma: a description of Richter's syndrome in eight dogs

Richter's syndrome (RS) is the development of an aggressive lymphoma in patients with chronic lymphocytic leukaemia (CLL). In humans, RS occurs in 2-20% of CLL, which transform into diffuse large B-cell lymphoma but reports in dogs are scarce. This study retrospectively describes eight dogs with CLL progressing into RS. A database including 153 dogs with CLL (93T CD8+ and 55 B-CLL) was interrogated and RS was demonstrated in eight cases (representing 5.2% of total CLL): two with T-cell (2.2% of T CLL) and six with a B-cell immunophenotype (10.9% of B-CLL). When RS occurred, lymphocytes were decreased compared to CLL. Five dogs had anaemia and two dogs thrombocytopenia. Frequent clinical signs included lymph node swelling, coughing, vomiting, neurological signs and weight loss. Independently from the therapy, RS was associated with a short survival (median 41 days). RS should be considered as an unfavourable evolution in canine CLL.