Treatment of myeloid neoplasia with doxorubicin and cytarabine in 11 dogs

Myelodysplastic syndrome (MDS) and acute myeloid leukaemia (AML) are primary myeloid neoplasms in dogs generally considered to have a poor outcome. In this study, we assessed toxicity, efficacy and outcome of concurrent administration of doxorubicin and cytarabine in 11 dogs with myeloid neoplasia. Bone marrow specimens were reviewed by three pathologists and classified as either MDS (n = 2), high grade MDS/early AML (MDS/AML; n = 4) or AML (n = 5). The median number of treatment cycles was 5 (range 1–9) and resolution of cytopenia was reported in 7 of 11 dogs including 2 dogs with MDS, 2 dogs with MDS/AML, and 3 dogs with AML. The median duration of remission in the seven responders was 344 days (range 109–1428) and the median overall survival for all dogs was 369 days. Adverse events consisted of predominantly low-grade gastrointestinal illness and myelosuppression. Three dogs developed grade V toxicity manifesting with heart failure (n = 2) at 369 and 1170 days after diagnosis and acute gastrointestinal side effects (n =1). Despite a limited sample size, these results suggest that a doxorubicin and cytarabine protocol may be considered as a therapeutic option in dogs with myeloid neoplasia. Protocol safety, in particular regarding myocardial toxicity, and efficacy should be further investigated.     

Proposed criteria for classification of acute myeloid leukemia in dogs and cats

Blood and bone marrow smears from 49 dogs and cats, believed to have myeloproliferative disorders (MPD), were examined by a panel of 10 clinical pathologists to develop proposals for classification of acute myeloid leukemia (AML) in these species. French-American-British (FAB) group and National Cancer Institute (NCI) workshop definitions and criteria developed for classification of AML in humans were adapted. Major modifications entailed revision of definitions of blast cells as applied to the dog and cat, broadening the scope of leukemia classification, and making provisions for differentiating erythremic myelosis and undifferentiated MPD. A consensus cytomorphologic diagnosis was reached in 39 (79.6%) cases comprising 26 of AML, 10 of myelodysplastic syndrome (MDS), and 3 of acute lymphoblastic leukemia (ALL). Diagnostic concordance for these diseases varied from 60 to 81% (mean 73.3 +/- 7.1%) and interobserver agreement ranged from 51.3 to 84.6% (mean 73.1 +/- 9.3%). Various subtypes of AML identified included Ml, M2, M4, M5a, M5b, and M6. Acute undifferentiated leukemia (AUL) was recognized as a specific entity. M3 was not encountered, but this subclass was retained as a diagnostic possibility. The designations M6Er and MDS-Er were introduced where the suffix "Er" indicated preponderance of erythroid component. Chief hematologic abnormalities included circulating blast cells in 98% of the cases, with 36.7% cases having >30% blast cells, and thrombocytopenia and anemia in approximately 86 to 88% of the cases. Bone marrow examination revealed panmyeloid dysplastic changes, particularly variable numbers of megaloblastoid rubriblasts and rubricytes in all AML subtypes and increased numbers of eosinophils in MDS. Cytochemical patterns of neutrophilic markers were evident in most cases of Ml and M2, while monocytic markers were primarily seen in M5a and M5b cases. It is proposed that well-prepared, Romanowsky-stained blood and bone marrow smears should be examined to determine blast cell types and percentages for cytomorphologic diagnosis of AML. Carefully selected areas of stained films presenting adequate cellular details should be used to count a minimum of 200 cells. In cases with borderline diagnosis, at least 500 cells should be counted. The identity of blast cells should be ascertained using appropriate cytochemical markers of neutrophilic, monocytic, and megakaryocytic differentiation. A blast cell count of > 30% in blood and/or bone marrow indicates AML or AUL, while a count of < 30% blasts in bone marrow suggests MDS, chronic myeloid leukemias, or even a leukemoid reaction. Myeloblasts, monoblasts, and megakaryoblasts comprise the blast cell count. The FAB approach with additional criteria should be used to distinguish AUL and various subtypes of AML (Ml to M7 and M6Er) and to differentiate MDS, MDS-ER, chronic myeloid leukemias, and leukemoid reaction. Bone marrow core biopsy and electron microscopy may be required to confirm the specific diagnosis. Immunophenotyping with lineage specific antibodies is in its infancy in veterinary medicine. Development of this technique is encouraged to establish an undisputed identity of blast cells. Validity of the proposed criteria needs to be substantiated in large prospective and retrospective studies. Similarly, clinical relevance of cytomorphologic, cytochemical, and immunophenotypic characterizations of AML in dogs and cats remains to be determined.     

Chronic granulocytic leukaemia in a dog with associated bacterial endocarditis, thrombocytopenia and preretinal and retinal haemorrhages

The clinical, haematological and pathological features of a case of chronic granulocytic leukaemia (CGL) associated with valvular bacterial endocarditis are described in a nine-year-old male Springer Spaniel. The disease was characterized clinically by lethargy, weight loss, hepatosplenomegaly, anaemia and leucocytosis. Severe thrombocytopenia resulted in preretinal and retinal haemorrhages. A diagnosis of CGL was based on the finding of a hypercellular bone marrow with increased M: E ratio and morphologically abnormal myeloid precursors. The dog terminally became leucopenic and bacteraemic. Necropsy revealed invasion of liver, spleen and bone marrow with a pleiomorphic population of myeloid blast cells, consistent with transition to a blast cell crisis.     

Acute myeloid leukaemia (M6B: pure acute erythroid leukaemia) in a Thoroughbred foal

A 10-week-old Thoroughbred filly was referred for anaemia of 4 weeks' duration. Haematology revealed severe anaemia and panleucopenia. Cytological examination of bone marrow smears revealed a myeloid to erythroid ratio <0.02:1 (reference range 0.5-2.4:1.0) and an abundance of erythroid precursor cells. The erythroid cell population included rubriblasts, prorubricytes and rubricytes, with only scant numbers of metarubricytes present. There were numerous mitotic erythroid cells, some of which were atypical and megaloblastic. These cytomorphological changes are consistent with pure acute erythroid leukaemia. No treatment was instituted and the filly died three days after presentation. This case illustrates the need to consider both haematology and bone marrow findings to establish a diagnosis of pure erythroid leukaemia. To our knowledge, there is no documented case of acute myeloproliferative disease in horses involving cells of erythroid lineage, but this condition should be considered a differential diagnosis for horses presenting with anaemia.     

In vitro selective suppression of feline myeloid colony formation is attributable to molecularly cloned strain of feline leukemia virus with unique long terminal repeat

Molecularly cloned feline leukemia virus (FeLV)-clone 33 (C-33), derived from a cat with acute myelocytic leukemia (AML), was examined to assess its relation to the pathogenesis of AML and myelodysplastic syndrome (MDS). To evaluate in vitro pathogenicity of FeLV C-33, bone marrow colony-forming assay was performed on marrow cells infected with FeLV C-33 or an FeLV subgroup A strain (61E, a molecularly cloned strain with minimal pathogenicity). The myeloid colony-forming activity of feline bone marrow mononuclear cells infected with FeLV C-33 was significantly lower than that of cells infected with 61E. This suggests that FeLV C-33 has myeloid lineage-specific pathogenicity for cats, and that FeLV C-33 infection is useful as an experimental model for investigating pathogenesis of MDS and AML.     

Myelodysplasia, hypophosphataemia, vitamin D and iron deficiency in an alpaca.

A pregnant 2-year-old alpaca was presented for evaluation of progressive weight loss, decreased appetite and lethargy that developed in winter. Haematologic and serum biochemical analyses revealed marked anaemia, leukopenia, severe hypophosphataemia and mild hypocalcaemia. Evaluation of bone marrow core biopsies and aspirates revealed an increased proportion of immature haematopoietic cells, without sufficient numbers of blast cells to be termed an acute myeloid leukaemia (AML). 1 The haematological and bone marrow findings were suggestive of myelodysplastic syndrome (MDS). The anaemia, leukopenia, lethargy and weight loss remained refractory to medical therapy and the alpaca was euthanased on humane grounds.     

Acute basophilic leukaemia in a three-month-old calf

A three-month-old female Holstein–Friesian calf was presented with acute tetraparesis. After neurological examination a multifocal lesion in the central nervous system was suspected with the most pronounced lesions between the third thoracic and the third lumbar vertebrae. Haematological examination revealed moderate anaemia as well as severe thrombocytopenia, neutropenia and leucocytosis. A blood smear and bone marrow aspirate exhibited predominantly blasts with basophilic granulation leading to a diagnosis of acute (myeloid) leukaemia with involvement of the basophilic lineage or an acute basophilic leukaemia. Magnetic resonance imaging revealed spinal cord compression; at necropsy, extensive localised haemorrhages extending into the thoracic vertebral canal were found. Histopathology revealed a large population of blast cells in several tissues including the meninges. Due to multifocal detection of neoplastic cells in the vascular system, neoplasia of the haematopoietic system was assumed in agreement with haematological findings. Signs of paresis could be explained by intramedullary spinal cord haemorrhage and myeloid infiltrations of meningeal vessels. In conclusion, despite its rarity, acute myeloid leukaemia with involvement of the basophilic lineage may be considered in diagnosing calves with progressive deteriorating general condition, paresis, leucocytosis with moderate basophilic differentiation or haemorrhagic disorders.     

Chronic granulocytic leukaemia/ eosinophilic leukaemia in a dog?

A suspected case of chronic granulocytic leukaemia (chronic myelogenous leukaemia) with eosinophil differentiation and hepatic involvement is described in a 3–5-year-old rottweiler dog. Neoplastic eosinophilic infiltrates were also present in the lungs, kidneys, mesenteric lymph nodes and peribronchial and prester-nal lymph nodes. Both pleural and abdominal effusions contained predominantly eosinophils and their precursors. The bone marrow showed an increase in the myeloid to erythroid ratio and an increase in the marrow granulocyte reserve. The majority of cells identified within the bone marrow were of the eosinophil series. Myelocytes and promyelocytes predominated.     

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. Frozenthawed cells stored in liquid nitrogen were also successfully cultured in vitro, but no permanent cell lines could be established.     

Does temporomandibular joint pathology affect performance in an equine athlete?

Temporomandibular joint (TMJ) pathology is a rarely reported cause of decreased performance among equine athletes or at least seldom recognised. This case report describes the work‐up of a high level dressage horse with decreased performance. Temporomandibular joint pathology was suspected based on computed tomography (CT) and the horse responded very well to joint treatment.     

Acute monocytic leukaemia in a cat

A three-year-old cat with lymphadenopathy, non-regenerative anaemia and marked leucocytosis (171.3 x 10(9) white blood cells/l) was diagnosed with monocytic leukaemia and treated with a combination of anticancer drugs. A number of mature and immature monocyte-like cells were detected in the peripheral blood and bone marrow; they proved to be monocytic cells by cytochemical examination and an analysis of their cell surface phenotype, indicating that the cat suffered from acute myeloid leukaemia, subclassified as monocytic leukaemia (M5). Treatment with cytarabine, doxorubicin, vincristine and prednisolone greatly reduced the number of blast cells in the cat's peripheral blood and bone marrow. The cat was in partial remission for 67 days and survived for 95 days after it was first examined.     

A retrospective review of acute myeloid leukaemia in 35 dogs diagnosed by a combination of morphologic findings,flow cytometric immunophenotyping and cytochemical staining results (2007‐2015)

Acute myeloid leukaemia (AML) is an uncommon, rapidly progressive neoplasm in dogs. The aim of this retrospective study was to characterize the clinical presentation, haematologic findings, diagnostic imaging results, treatment and survival time of a contemporary cohort of dogs with AML. Diagnosis was based on >20% blasts in bone marrow or blood identified as myeloid based on morphologic findings, flow cytometric immunophenotyping and cytochemical staining. Medical records of 35 dogs diagnosed with AML from 2007 to 2015 were included. Most dogs presented with inappetence (66%) and lethargy (57%) and physical examination findings of peripheral lymphadenopathy (74%) and tachypnea (62%). Common haematologic findings were quantifiable circulating blasts (85%; median blast count 35 700/μL; range: 300‐276 500/μL), anaemia (median haematocrit 34%; range: 11%‐52%) and thrombocytopenia (median 57 000/μL; range: 9000‐252 000/μL). Bicytopenia and pancytopenia were each found in 44% of dogs. Follow‐up information was available for 34 dogs. The overall median survival time from diagnosis was 19 days (range: 1‐121 days). Clinical progression in some dogs was not as rapid as previously reported. Haematologic responses to various chemotherapeutics were documented in 3 dogs, with associated survival times of 62, 103 and 121 days. Dogs treated with prednisone or a combination of chemotherapy and prednisone had improved survival compared to dogs that received symptomatic care only (P < .0001). Our results show canine AML has an overlapping clinical presentation with lymphoma. The prognosis for canine AML remains extremely guarded. Further studies are needed to optimize therapeutic regimens for dogs with AML.     

Surgical site infection after occlusion of the internal carotid artery with a thrombectomy catheter: Five cases

Although rare, guttural pouch mycosis is a potentially life-threatening disease in the horse. The disease is most commonly treated surgically. One surgical option is occlusion of the internal carotid artery with a combination of ligation and use of a balloon tipped venous thrombectomy catheter. Complications of such treatment are rarely reported. This case series of five individuals describes the appearance, diagnosis and management of medium (>2 weeks) and long-term (>10 years) complications (including abscess formation, draining sinuses and wound dehiscence) of internal carotid artery occlusion with a venous thrombectomy catheter and management of these surgical site infections. The clinical presentations included swelling and/or discharging tracts in the parotid region. In one horse, an osseous reaction of the basisphenoid bone and penetration of the contralateral guttural pouch by the implant were identified by computed tomography. In all five horses, the surgical site infections were successfully resolved following removal of the venous thrombectomy catheter.     

Myeloid and Megakaryocytic Hypoplasia in Related Standardbreds

Myeloid and megakaryocytic bone marrow hypoplasia in association with moderate to profound neutropenia was observed in 8 young Standardbred horses sired by the same stallion; 7 horses were intermittently thrombocytopenic. Evaluation of serial neutrophil counts in 2 horses suggested that a cyclic variation in neutrophil numbers was present, that lymphocyte numbers increased when neutrophil counts decreased, and that platelet counts decreased when neutrophil counts decreased. Preliminary bone marrow cultures indicated that myeloid progenitor cells were present and that these cells were able to respond to exogenous growth factors by differentiating. A bone marrow microenvironment or growth factor defect is suspected. Seven of 8 horses died or were euthanized. One horse with moderate neutropenia and a normal platelet count has been racing for 3 years. Necropsies in 4 horses did not reveal a cause for the myeloid hypoplasia. A familial basis for the disease is suspected.     

Idiopathic effusive pericarditis with tamponade in the horse

Pericarditis and pericardial effusion are considered to occur rarely in the horse. The clinical and laboratory features of idiopathic pericarditis with effusion diagnosed in 10 horses over a seven-year period were reviewed. Consistent physical findings included tachycardia, ventral oedema, jugular venous distention and diminished heart sounds. Electrocardiographic features included diminished voltages and electrical alternans, and the effusion was identified by echocardiography in the six horses in which it was performed. Pericardiocentesis relieved clinical signs in nine horses. Laboratory analysis of pericardial fluid samples classified six cases as aseptic serofibrinous, three cases as eosinophilic, and one case as histiocytic. One horse died and three were destroyed. The remaining six horses recovered following pericardiocentesis (performed once or twice) with or without corticosteroid treatment, and were alive one month to seven years after diagnosis.     

Classification of myeloid neoplasms: a comparative review

Classification of myeloid neoplasms in veterinary medicine was modeled in the early 1990s after French-American-British and National Cancer Institute systems used in human medicine. Recently our physician counterparts, in collaboration with oncologists, constructed a new World Health Organization (WHO) standard. WHO revisions lower the blast threshold from 30% to 20% for diagnosing acute myeloid leukemia (AML) and expand and redefine AML categories. AML is now subdivided into 4 broad groups: 1) AML with recurrent genetic abnormalities, 2) AML with multilineage dysplasia, 3) AML with previous chemotherapy and/or radiation, and 4) AML, not otherwise categorized. AML alphanumeric designations (M1, M2, etc) have been discontinued as numbers of subtypes have increased. The lower blast percentage eliminates one category of myelodysplastic syndrome (MDS): refractory anemia with excess blasts in transformation. A new MDS category was created: refractory cytopenia with multilineage dysplasia (RCMD), with lineage dysplasia assessed using newly defined percentage limits. At least 10% of cells from each of 2 lineages must display atypia for a diagnosis of RCMD. That threshold is 50% for diagnosing AML with multilineage dysplasia. Chronic myelomonocytic leukemia has been removed from the MDS category and included in a new category of diseases that have features of both MDS and chronic leukemia. WHO revisions are a signal to veterinary clinical pathologists to assess the validity of our system, which was built on premises now questioned.     

Clonality analysis of various hematopoietic disorders in cats naturally infected with feline leukemia virus

The clonality analysis of the bone marrow cells was carried out by detecting the integrated proviruses of feline leukemia virus (FeLV) to understand the pathogenesis of FeLV-associated hematopoietic disorders in cats. Bone marrow cells from 4 cases with acute myeloid leukemia (AML), 9 cases with myelodysplastic syndromes (MDS), 2 cases with pure red cell aplasia (PRCA) and 3 healthy carriers infected with FeLV were subjected to Southern blot analyses using an exogenous FeLV probe. Clonal hematopoiesis was found in all the cases with AML and in 6 of the 9 cases with MDS, but not in the cases with both PRCA and healthy carriers infected with FeLV. In the 2 cases with MDS, it was thought that the same clones of the hematopoietic cells might proliferate before and after the progression of the disease irrespective of the changes of the hematological diagnoses by cytological examination. This study indicates that MDS in cats is a disease manifestation as a result of clonal proliferation of hematopoietic cells and can be recognized as a pre-leukemic state of AML.     

Pancytopenia Secondary to Lymphoid Leukemia in Three Horses

Pancytopenia was observed in two 3-year-old geldings and one 11-year-old mare. All horses had a brief history (2 days to 4 weeks) of fever, anorexia, and depression. One of the three horses had blast cells present on a peripheral blood smear. Examination of the bone marrow showed substantial infiltration with neoplastic lymphoid cells. At necropsy, neoplastic cells were restricted to the bone marrow in one horse, present in bone marrow, liver, and spleen in the second horse, and reported in multiple tissues in the third horse, including bone marrow, kidneys, lung, myocardium and lymph nodes. The value of a bone marrow aspirate and core biopsy in the investigation of pancytopenia is highlighted. (Journal of Veterinary Internal Medicine 1993; 7:360–363. Copyright © 1993 by the American College of Veterinary Internal Medicine.)     

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.     

Bone marrow necrosis and myelophthisis: manifestations of T‐cell lymphoma in a horse

Abstract: A 14‐year‐old spayed American Paint mare was evaluated for mild colic, anorexia, pyrexia, and pancytopenia. Physical examination revealed mild tachycardia, tachypnea, and pale mucous membranes. Serial laboratory analyses revealed progressive pancytopenia, hyperfibrinogenemia, and hyperglobulinemia. A few large atypical cells were observed in peripheral blood smears. Results of tests for equine infectious anemia and antipenicillin antibody were negative. Serum protein electrophoresis indicated a polyclonal gammopathy. Smears of bone marrow aspirates contained hypercellular particles, but cell lines could not be identified because the cells were karyolytic, with pale basophilic smudged nuclei and lack of cellular detail. A diagnosis of bone marrow necrosis was made. Treatment consisted of antimicrobials, nonsteroidal anti‐inflammatory drugs, and corticosteroids. The pyrexia resolved; however, the pancytopenia progressively worsened and petechiation and epistaxis developed. The horse was humanely euthanized. Postmortem examination revealed a diffuse round cell neoplasm infiltrating the kidneys, spleen, lymph nodes, lungs, and bone marrow. Immunophenotyping results (CD3+, CD79α−) indicated the neoplastic cells were of T‐cell lineage. Infiltration of lymphoma cells into the bone marrow appeared to have resulted in severe myelophthisis and bone marrow necrosis. Bone marrow necrosis has been associated previously with lymphoma in humans and dogs. To our knowledge, this is the first reported case of lymphoma resulting in bone marrow necrosis in a horse.