Acute myelomonocytic leukemia with multifocal manifestation and spinal cord infiltration in a dog.

INTRODUCTION: Few cases of myelomonocytic leukemia associated with neurological signs have been described in dogs; none have been related to intraparenchymal spinal cord infiltration by neoplastic cells. This short communication describes a case of acute myelomonocytic leukemia subtype M4 in a dog with spinal cord infiltration. A 3-year-old male Golden Retriever was presented with a history of hyperthermia, lymphadenomegaly, leukocytosis with circulating blast cells, anemia and thrombocytopenia, and acute onset paraplegia. Immunophenotyping of peripheral blood by flow cytometry was consistent with acute myelomonocytic leukemia subtype M4. The dog was euthanized because of clinical deterioration and unfavourable prognosis. Postmortem examination revealed multi-organ neoplastic infiltration, including the spinal cord. To our knowledge, this is the first case of acute myelomonocytic leukemia subtype M4 in a dog with spinal cord infiltration. Our findings hold importance for including myelomonocytic leukemia in the differential diagnosis of patients with neurological signs due to spinal cord localisation.

INTRODUCTION: Peu de cas de leucémie myélomonocytaire associés à des signes neurologiques ont été décrits chez le chien ; aucun n'était lié à une infiltration intraparenchymateuse de la moelle épinière par des cellules néoplasiques. Cette courte communication décrit un cas de leucémie aiguë myélomonocytaire de sous-type M4 chez un chien avec infiltration de la moelle épinière. Un Golden Retriever mâle de 3 ans a été présenté avec une anamnèse d'hyperthermie, de lymphadénomégalie, de leucocytose avec des cellules blastiques circulantes, d'anémie et de thrombocytopénie et de paraplégie d'apparition aiguë. L'immunophénotypage du sang périphérique par cytométrie de flux était compatible avec une leucémie myélomonocytaire aiguë de sous-type M4. Le chien a été euthanasié en raison de la détérioration de son état clinique et du pronostic défavorable. L'examen post-mortem a révélé une infiltration néoplasique multi-organique, y compris la moelle épinière. À notre connaissance, il s'agit du premier cas de leucémie aiguë myélomonocytaire de sous-type M4 chez un chien avec infiltration de la moelle épinière. Nos résultats sont importants pour inclure la leucémie myélomonocytaire dans le diagnostic différentiel chez les patients présentant des signes neurologiques dus à une localisation médullaire.

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.

A clinical case of acute myelomonocytic leukemia in a Holstein cow.

A 2-year, 3-month-old Holstein cow presented with anorexia and enlarged superficial lymph nodes. Fine needle aspiration cytology of the superficial lymph nodes revealed large blast cells. Hematological examination revealed anemia, neutropenia, and blast cells in peripheral blood. Blast cells were the predominant cell type in bone marrow aspirates. Of the non-erythroid cells, 26%, 58%, and 18% were positive for myeloperoxidase, α-naphthyl acetate esterase, and naphthol AS-D chloroacetate esterase, respectively. Pathological examination revealed the proliferation of neoplastic cells, which were positive for monocytic markers, in the affected lymph nodes. The cow was diagnosed with acute myelomonocytic leukemia based on these findings. This report highlights the importance of performing bone marrow aspiration cytology and cytochemical staining when diagnosing bovine myeloid leukemia.

Acute myelomonocytic leukemia (AML-M4) in a dog with the extradural lesion.

A two-year-old dog having presented with neurological signs showed marked leukocytosis and appearance of blast cells in the peripheral blood. Hematological and bone marrow examination showed an increase in blasts having both myeloid and monocytic cells characteristics. The dog was diagnosed with acute myelomonocytic leukemia (AML-M4) on the basis of bone marrow findings. Although the dog was treated with a multi-combination chemotherapy, the neurological abnormalities progressed and the dog was euthanized. Myelographic examination and necropsy revealed the extradural lesion formed by AML-M4 around the cervical spinal cord and this lesion was considered as a cause of the neurological signs.

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 leukaemia with short-term spontaneous remission in a cat.

A 2-year-old, spayed female domestic shorthair cat was referred with a history of anorexia and depression of 1 week duration. On physical examination, the cat was lethargic and febrile, with splenomegaly, anisocoria and ulcerative stomatitis. A complete blood count (CBC) and a biochemistry profile showed leukocytosis, numerous blast cells in the peripheral blood, thrombocytopenia, hyperglobulinaemia and a positive test for feline leukaemia virus antigen. A diagnosis of acute myelomonocytic leukaemia was made on the basis of the results of bone marrow cytology, histopathology, and immunochemistry (CD3, CD79a, lysozyme, and myeloperoxidase) tests. Following an unexpected 1-month period of clinical and clinicopathological remission without chemotherapy, the cat relapsed and died 1 week later.

A potentially misleading presentation and course of acute myelomonocytic leukemia in a dog.

A nine-year-old, castrated male golden retriever had lethargy, fever, massive peripheral lymphadenomegaly, hepatosplenomegaly, and pale mucous membranes. There was a marked leukocytosis (456.3 x 10(3) cells/microliter) with 99% blasts; a moderate, nonregenerative anemia; and marked thrombocytopenia. A tentative diagnosis of acute lymphocytic leukemia was made pending results of cytochemical staining. Despite the severity of the laboratory and clinical findings, the dog exhibited a partial response to an induction chemotherapy protocol commonly used for lymphoma. Subsequent cytochemical staining of the original blood and bone-marrow samples resulted in a revised diagnosis of acute myelomonocytic leukemia (AML-M4). Clinicopathological findings, response to treatment, and clinical outcome in this case of canine AML-M4 are discussed.

Intravascular leukostasis and systemic aspergillosis in a horse with subleukemic acute myelomonocytic leukemia.

Leukemia is a neoplastic disease of one or more of the cell types of the hemopoietic system and is rarely diagnosed in the horse. This report describes a case of subleukemic acute myelomonocytic leukemia in an 11-year-old gelding. Preliminary cytological diagnosis was supported by two types of laboratory investigations. Cytochemical characterization of blood and bone marrow neoplastic cells was consistent with a myelomonocytic origin. Neoplastic blast cells in peripheral blood were labeled by monoclonal antibodies specific for cell surface molecules of horse granulocytes, but they were not labeled by antibodies to T- or B-lymphocytes or macrophages. Treatment was attempted but was unsuccessful. At necropsy, intravascular leukostasis was present in all tissues examined. Fungal hyphae were also found in lung interstitium and colonic submucosa, suggesting the presence of a systemic mycosis. Nucleated cells were isolated from peripheral blood and cultured in vitro; they survived for up to 2 weeks and had evidence of cell division that was not sustained. Frozen-thawed cells stored in liquid nitrogen were also successfully cultured in vitro, but no permanent cell lines could be established.

Acute myelomonocytic leukemia in a calf.

In a 2-month-old crossbred calf with paraplegia, results of neurologic evaluation were suggestive of a spinal cord lesion caudal to L3. The calf bled from the blood sampling site for an extended period after venipuncture. Leukocytosis, anemia, and thrombocytopenia were observed. The leukocytes were predominantly atypical blast cells. Postmortem examination revealed petechial hemorrhages throughout the internal organs. Bone marrow was pale tan, with no red marrow seen. Atypical leukocytes were diffusely distributed throughout the body, with penetration of the spinal cord and spinal roots, particularly in the lumbar region. Atypical leukocytes stained positively for alpha-naphthyl acetate esterase and chloracetate esterase, and stained with Sudan black B. Atypical leukocytes expressed class-1 and class-2 major histocompatability antigens, but did not express specific T-, B-, or null-cell surface antigens. The final diagnosis was myelomonocytic leukemia. Differential diagnosis of leukemia in calves should include myelogenous leukemia, and requires use of various techniques to make a definitive diagnosis.