Suspected myelodysplastic/myeloproliferative neoplasm in a feline leukemia virus-negative cat.

A 10-year-old castrated Domestic Short-Haired cat was presented to a primary care veterinarian for a wellness examination and laboratory examination for monitoring of diabetes mellitus. The CBC revealed marked thrombocytosis, leukopenia and macrocytic, normochromic anemia. The cat tested negative for FeLV and feline immunodeficiency virus, but was positive for Mycoplasma haemominutum by PCR. Hematologic abnormalities were not responsive to therapy, so a repeat CBC and a bone marrow aspiration for cytology were performed. Additional blood smear findings included anisocytosis with megaloblastic erythroid precursors, large platelets, eosinophilic myelocytes and metamyelocytes, and rare unidentified blasts. The bone marrow smear was highly cellular, and the cytologic pattern was consistent with myelodysplastic syndrome with an erythroid predominance. At that time, 15% blasts were present. The cat was treated with a vitamin K2 analog, doxycycline, and prednisolone, but without a clinical response. Within 3 months, euthanasia was elected due to declining quality of life, and a necropsy was performed. Postmortem bone marrow smears were highly cellular and dominated by monomorphic blasts of unknown line of origin (52%), persistent marked erythroid and megakaryocytic dysplasia, and ineffective erythropoiesis and granulopoiesis. Immunohistochemical, immunocytochemical, and cytochemical stains resulted in a diagnosis of acute myeloid leukemia of unclassified type. Additional histologic findings included mixed hepatitis with trematode infestation and lymphoplasmacytic interstitial nephritis with fibrosis. The marked thrombocytosis with myelodysplastic syndrome and the FeLV-negative status of this cat were unusual. The difficulty in classifying the myelodysplasia and subsequent leukemia highlights a need for further reporting and characterization of these types of disease.

Flow cytometric immunophenotyping of feline bone marrow cells and haematopoietic progenitor cells using anti-human antibodies.

There is a paucity of species-specific antibodies available for feline haematopoietic conditions. The purpose of this study was to broaden the panel of antibodies available for use in the immunophenotypic characterisation of feline haematopoietic cells by testing clones of anti-human monoclonal antibodies (mAbs) on normal, neoplastic and cultured feline haematopoietic progenitors to determine cross-reactivity to feline counterparts. In this study, 24 clones of anti-human mAbs were tested on normal or neoplastic feline bone marrow and peripheral blood cells. Six of these mAbs, including anti-cluster of differentiation (CD)61, anti-CD18, anti-CD14, anti-CD235a, anti-CD41 and anti-CD29, cross-reacted with normal feline bone marrow cells, whereas anti-CD33 and anti-CD117 cross-reacted with the blast cells in the bone marrow of two cats with myelodysplastic syndrome, and anti-CD71, anti-235a, anti-41 and anti-42 cross-reacted with immature erythroid cells in a cat with erythroleukaemia. In a feline immunodeficiency virus-positive cat, bone marrow cells were labelled with anti-CD33, anti-14 and anti-45. Anti-CD18, anti-CD14, anti-CD41 and anti-CD61 also reacted with the peripheral blood cells of the healthy cats. The feline haematopoietic progenitors formed colonies in the methylcellulose-based semisolid medium with significant enrichment of colony-forming unit-granulocyte, monocyte and burst-forming unit-erythroid. A panel of six anti-feline mAbs (anti-CD21-like, anti-T lymphocytes, anti-CD172a, anti-granulocyte, anti-CD45-like and anti-CD18) and eight anti-human antibodies (anti-CD71, anti-CD33, anti-CD235a, anti-CD41, anti-CD61, anti-CD117, anti-CD38 and anti-CD34) were used for the immunophenotypic characterisation of the feline bone marrow progenitors. CD45, CD33, CD235a and CD18 were expressed by the feline haematopoietic progenitor cells, with the highest expression level for CD45.

Prognostic markers for myeloid neoplasms: a comparative review of the literature and goals for future investigation.

Myeloid neoplasms include cancers associated with both rapid (acute myeloid leukemias) and gradual (myelodysplastic syndromes and myeloproliferative neoplasms) disease progression. Percentage of blast cells in marrow is used to separate acute (rapid) from chronic (gradual) and is the most consistently applied prognostic marker in veterinary medicine. However, since there is marked variation in tumor progression within groups, there is a need for more complex schemes to stratify animals into specific risk groups. In people with acute myeloid leukemia (AML), pretreatment karyotyping and molecular genetic analysis have greater utility as prognostic markers than morphologic and immunologic phenotypes. Karyotyping is not available as a prognostic marker for AML in dogs and cats, but progress in molecular genetics has created optimism about the eventual ability of veterinarians to discern conditions potentially responsive to medical intervention. In people with myelodysplastic syndromes (MDS), detailed prognostic scoring systems have been devised that use various combinations of blast cell percentage, hematocrit, platelet counts, unilineal versus multilineal cytopenias and dysplasia, karyotype, gender, age, immunophenotype, transfusion dependence, and colony-forming assays. Predictors of outcome for animals with MDS have been limited to blast cell percentage, anemia versus multilineal cytopenias, and morphologic phenotype. Prognostic markers for myeloproliferative neoplasms (eg, polycythemia vera, essential thrombocythemia) include clinical and hematological factors and in people also include cytogenetics and molecular genetics. Validation of prognostic markers for myeloid neoplasms in animals has been thwarted by the lack of a large case series that requires cooperation across institutions and veterinary specialties. Future progress requires overcoming these barriers.