Acute myelomonocytic leukemia in a dog

Cytochemical stains and morphologic characteristics were essential in making the correct diagnosis in a dog with acute myelomonocytic leukemia, which initially was diagnosed as lymphoblastic leukemia. Response to a treatment regimen of cytosine arabinoside, thioguanine, vincristine, and doxorubicin, besides accomplishing complete remission, helped revise the initial diagnosis to acute myelomonocytic leukemia. After remission was achieved, the dog died of a fulminating viral infection.     

Acute myelomonocytic leukemia with neurologic manifestations in the dog

A dog was presented with mandibular paralysis, photophobia, and diffuse atrophy of the cranial skeletal muscles. Physical examination also revealed glossal paralysis, reduction of the swallowing reflex, reduction of the pupillary light response, and generalized lymphadenopathy. Cytologic and ultrastructural examinations of blood films, bone marrow, and lymph node aspirates were consistent with acute myelomonocytic leukemia. Post-mortem examination revealed extensive, multisystemic neoplastic infiltration with marked involvement of the central and peripheral nervous systems, especially the cranial and lumbar spinal nerves and associated ganglia. Neurologic manifestations are unusual in acute myelomonocytic leukemia in the dog.     

Acute myelomonocytic leukemia manifested as myelophthisic anemia in a dog.

A 10-year-old, Golden Retriever-type castrated male dog was found to have a hemogram consistent with myelophthisic anemia. Within 30 days the hemogram changed in such a manner that a myeloproliferative disorder was evident. On the basis of hematologic, cytochemical, and cytologic findings, acute myelomonocytic leukemia was diagnosed.     

A dog with acute myelomonocytic leukemia

A three-year-old dog with marked leukocytosis, lymphadenopathy, and diarrhea showed an increase in unidentified blasts in the peripheral blood, and they were proliferated in the bone marrow. The dog was diagnosed with myelomonocytic leukemia (M4) because the blast cells were demonstrated by cytochemical staining to be both myeloid and monocytic cells. Although the dog was treated with a multi-combination chemotherapy and induction therapy using vitamin K2, it died on day 47 after the first admission. This case is the first report of M4 in Japan.     

Acute myelomonocytic leukemia in a horse

A 7-year-old Quarter Horse stallion with a myeloproliferative disorder was examined because of colic, and an enterolith was removed surgically. The horse experienced secondary complications after abdominal surgery, and leukopenia and thrombocytopenia were detected. Five months later, the horse was examined for recurrent peripheral edema and for repair of an abdominal incisional hernia. Acute myelomonocytic leukemia was diagnosed, and treatment with low-dose (noncytocidal) cytosine arabinoside was unsuccessful. Necropsy revealed neoplastic infiltrate in the spleen, liver, lung, adrenal gland, testes, and eye. The persistent hematologic abnormalities before the onset of overt leukemia may represent hematopoietic dysplasia or preleukemia.     

Spontaneous acute erythroblastic leukaemia (AML-M6Er) in a dog

A five-year-old golden retriever was presented with anaemia, thrombocytopenia, anorexia and lethargy. Peripheral blood cytology showed abnormal cells similar to proerythroblasts with multiple nucleoli and strongly basophilic cytoplasm. Bone marrow cytopathology revealed that the blast cells accounted for more than 80% of all nucleated cells (ANC). These blast cells were confirmed as erythroblastic cells by cytochemistry, polymerase chain reaction for genetic clonality assessment of IgH and TCRγ, flow cytometry, and transmission electron microscopy. Based on these observations, the dog was diagnosed with acute erythroblastic leukaemia (AML-M6Er). Chemotherapy with cytarabine commenced on day 7 after initial presentation, but the dog died 2 days later. This is the first report of spontaneous AML-M6Er in a dog.     

A dog with myelodysplastic syndrome: chronic myelomonocytic leukemia

An eleven-year-old female pug was referred to Yamaguchi University Animal Hospital for evaluation of anemia and thrombocytopenia. The cytological examination of the peripheral blood showed some giant monocytic lineage blast cells. A few granulocytes and platelets had dysplastic features. On day 7, in addition to increasing the monocytic lineage cells, the dysplastic features of the blood had also increased compared to the initial examination. We performed bone marrow aspiration upon her death. The bone marrow revealed dysplastic features in all three hematopoietic cell lines, and an increase in the monocytic cell line. Based on the features of the bone marrow and the peripheral blood, this case was confirmed to be myelodysplastic syndrome--Chronic myelomonocytic leukaemia (MDS-CMML).     

Acute nonlymphocytic leukemia in a dog

Acute nonlymphocytic leukemia was diagnosed in a 1-year-old Rhodesian Ridgeback. Clinical signs of disease included weight loss, anorexia, lethargy, lymphadenopathy, splenomegaly, and hepatomegaly. Doxorubicin was administered IV on day 4 at a dosage of 30 mg/m2 of body surface, followed 2 days later by oral administration of cyclophosphamide at a dosage of 100 mg/m2. The cyclophosphamide was given for 4 consecutive days (days 8, 9, 10, and 11), but the WBC count did not respond. The dog was administered 500 ml of blood; but on day 12, it died. Necropsy was not performed, but the presumptive cause of death was related to leukostasis.     

Acute megakaryoblastic leukemia with erythrophagocytosis and thrombosis in a dog

A 7-year-old, intact male Dachshund was presented to the Lyon veterinary school for lethargy and anorexia of several weeks duration. The main clinical signs were pale and icteric mucous membranes, hepatomegaly, splenomegaly, and lymphadenopathy. Results of a CBC and plasma biochemistry tests revealed severe nonregenerative anemia, thrombocytopenia, and increased alanine aminotransferase and alkaline phosphatase activities. Blood smear evaluation and cytologic examination of lymph node and bone marrow aspirate specimens revealed a large population of poorly differentiated blast cells with morphologic features suggesting megakaryocytic lineage. A low number of well-differentiated but dysplastic megakaryocytes also were observed in lymph node and bone marrow smears. A few blast cells were erythrophagocytic. Blast cells were positive for glycoprotein IIIa, factor VIII-related antigen, and factor XIII using immunocytochemistry. The dog was euthanized and necropsied. Histologic findings consisted of diffuse, massive infiltration of lymph nodes, liver, and spleen by megakaryoblasts and atypical megakaryocytes, with widespread thrombosis. This case confirms the usefulness of immunochemistry, including for factor XIII, in the diagnosis of megakaryoblastic leukemia, and demonstrates the unique features of tumor cell erythrophagocytosis and marked fibrinous thrombosis, which have not been reported previously in dogs.     

Acute myeloblastic leukemia with associated BCR-ABL translocation in a dog

An 8-year-old male neutered Labrador Retriever was referred to the University of Wisconsin Veterinary Medical Teaching Hospital with a presumptive diagnosis of leukemia. Hematologic abnormalities included normal neutrophil count with a left shift, monocytosis, eosinophilia, thrombocytopenia, and circulating immature mononuclear cells. Bone marrow was effaced by immature hematopoietic cells of various morphologic appearances. In addition, large multinucleated cells were observed frequently. Flow cytometric analysis of nucleated cells in blood revealed 34% CD34(+) cells, consistent with acute leukemia. By immunocytochemical analysis of cells in blood and bone marrow, some mononuclear cells expressed CD18, myeloperoxidase, and CD11b, indicating myeloid origin; some, but not all, large multinucleated cells expressed CD117 and CD42b, the latter supporting megakaryocytic lineage. The diagnosis was acute myeloblastic leukemia without maturation (AML-M1). To identify genetic aberrations associated with this malignancy, cells from formalin-fixed paraffin-embedded bone marrow were analyzed cytogenetically by multicolor fluorescence in situ hybridization (FISH). Co-localization of bacterial artificial chromosome (BAC) containing BCR and ABL was evident in 32% of cells. This confirmed the presence of the canine BCR-ABL translocation or Raleigh chromosome. In people, the analogous translocation or Philadelphia chromosome is characteristic of chronic myelogenous leukemia (CML) and is rarely reported in AML. BCR-ABL translocation also has been identified in dogs with CML; however, to our knowledge this is the first report of AML with a BCR-ABL translocation in a domestic animal.     

Acute megakaryoblastic leukemia in a German Shepherd dog

Abstract: An 11‐year‐old spayed‐female German Shepherd dog was presented to the Veterinary Medical Teaching Hospital at Kansas State University with a history of weight loss, anorexia, depression, and lethargy for 2–3 weeks. Radiographic examination revealed a mass in the spleen and several round radiodense foci in the liver. CBC results included normocytic normochromic anemia, marked thrombocytopenia, and low numbers of neoplastic cells that frequently had cytoplasmic projections or blebs. A bone marrow aspirate contained about 80% neoplastic megakaryoblasts with the same microscopic features as those observed in peripheral blood. Using flow cytometry, cells of large size were identified in peripheral blood that expressed CD41/61, CD45, CD61, and CD62P (P‐selectin) and were negative for markers of T cells, B cells, monocyte/macrophages, and dendritic cells. Because of the poor prognosis, euthanasia and subsequently necropsy were performed. On histopathologic examination, neoplastic megakaryoblasts were identified in spleen, liver, mesenteric lymph node, and the pulmonary vasculature. Using immunohistochemistry, the neoplastic megakaryoblasts weakly expressed von Willebrand factor. Based on microscopic and immunophenotypic findings, a diagnosis of acute megakaryoblastic leukemia (AMegL) was made. To our knowledge, this is the first report of AMegL in a domestic animal in which immunophenotyping by flow cytometry and a panel of antibodies against CD41/61, CD61, and CD62P were used to support the diagnosis.     

Myelodysplastic changes in a cat with myelomonocytic leukemia

Submandibular and/or disseminated zygomycosis (mucormycosis) was diagnosed in 3 feeder pigs from 2 farrow-to-finish farms. Affected pigs were stunted and unthrifty. Each pig had a large unilateral submandibular granuloma replacing the mandibular lymph node on the affected side. Two pigs had disseminated lesions. One had an abscess on the serosa of the stomach; another had abscesses scattered throughout the liver and mesenteric lymph nodes. Impression smears were made of several masses and stained with blue-black ink. Examination of smears by light microscopy revealed coarse, infrequently septate, irregularly branching, mucoraceous fungi typical of a Zygomycete. Histologic examination of the submandibular masses revealed granulomas containing large numbers of mixed inflammatory cells, including giant cells. Mesenteric lymph nodes and liver abscesses had necrotic cores surrounded by fibrous capsules infiltrated by mixed inflammatory cells. Hyphae of a mucoraceous fungus were scattered throughout all masses. The 2 pigs submitted alive had marked serum hypoproteinemia, including hypoglobulinemia.     

Pulmonary aspergillosis in a horse with myelomonocytic leukemia

Acute myelomonocytic leukemia was diagnosed in a 2-year-old Standardbred mare that had hind limb edema and fever unresponsive to antibiotics. The mare had anemia, thrombocytopenia, and leukocytosis, with circulating myeloblasts and monocytoid cells. A bone marrow specimen was hypercellular, with myeloblasts and monocytoid cells. Peroxidase, chloroacetate esterase, and alpha naphthyl acetate esterase activities were detected in many bone marrow cells. Interstitial pulmonary densities were seen radiographically. The mare was euthanatized and necropsied. Infiltrates of leukemic cells were found microscopically in specimens of spleen, lymph nodes, liver, kidneys, gastrointestinal tract, and lungs. Granulomas containing fungal hyphae were seen microscopically in the lungs, and Aspergillus sp was isolated from the lesions.     

Chronic myelomonocytic leukemia in a cat

A 1-year-old spayed domestic short-haired cat was referred with anorexia and weight loss. Hematologic findings indicated nonregenerative anemia, severe neutropenia and monocytosis. The feline leukemia virus (FeLV) antigen test was positive reaction by enzyme-linked immunosorbent assay. Dysgranulopoiesis with slight increase in blast cells were observed in bone marrow smears. On the basis of blood and bone marrow findings, the cat was diagnosed as chronic myelomonocytic leukemia (CMMoL), which possibly corresponds to a kind of the subtypes in human myelodysplastic syndrome (MDS).     

Acute myelomonocytic leukemia negative for alpha-naphthyl acetate esterase stain in a Holstein cow

A 4-year, 7-month-old Holstein cow presented with anorexia. Physical examination revealed masses in the interscapular region and vagina. Blast cells were detected in the masses and peripheral blood by fine needle aspiration cytology and hematological examination. By bone marrow aspiration, blast cells constituted up to 24.2% of all nucleated cells, and 22% and 2% of non-erythroid cells stained positive for myeloperoxidase and alpha-naphthyl acetate esterase (ANAE), respectively. Pathological examination revealed the mass lesions consisted of a proliferation of tumor cells, which were positive for monocytic markers (HLA-DR and Iba-1). The cow was diagnosed with acute myelomonocytic leukemia (AMML). Even when tumor cells are ANAE-negative, AMML cannot be completely ruled out and should be considered when diagnosing cattle with leukemia/lymphoma.     

Lymphoid leukemia in the dog. Acute lymphoblastic leukemia and chronic lymphocytic leukemia

True lymphoid leukemia of bone-marrow origin may present as two distinct clinical forms in the dog. Acute lymphoblastic leukemia is a rapidly progressive disease associated with proliferation of malignant, undifferentiated lymphoblasts. Chronic lymphocytic leukemia is a more insidious form of malignancy associated with abnormal proliferation of small lymphocytes. Recognition of these clinically distinct forms of leukemia and their differentiation from lymphosarcoma are important in considering prognosis and approach to therapy.