Thymic lymphosarcoma of T cell lineage in a koala (Phascolarctos cinereus)

Objective To diagnose and characterise thymic lymphosarcoma in a koala.
Design A pathological case.  

Animal

Seven-year-old female koala.
Procedure The neoplastic process was investigated macroscopically, haematologically, histologically and immunohistologically.
Results The koala had difficulty swallowing because of a medial swelling in the lower neck. Biopsy of this mass and blood examination revealed lymphosarcoma with a leukaemic manifestation; necropsy and histopathological examination showed the mass to be thymus. Palatine tonsils, cervical, axillary and mesenteric lymph nodes, spleen, liver, gut, bronchi, genitalia and bone marrow were infiltrated by neoplastic cells. Immunohistological staining of the thymic mass, cervical and mesenteric lymph nodes, bone marrow, spleen and gut revealed the neoplastic cells to be of T lymphocyte origin (positive for both anti-human CD3 and CD5).  

Conclusions

It is speculated that the neoplastic process originated in the thymus and was disseminated by bloodborne neoplastic cells: This first report of thymic lymphosarcoma in a marsupial confirms that antibodies raised originally to investigate human lymphoid neoplasia can cross-react with neoplastic lymphocytes in koalas.     

Diagnosis and treatment of chronic T-lymphocytic leukemia in a spotted hyena (Crocuta crocuta).

Physical examination of an asymptomatic 20-yr-old intact female spotted hyena (Crocuta crocuta) revealed a midabdominal mass. A complete blood count (CBC) revealed peripheral lymphocytosis. Abdominal ultrasonography and laparoscopy confirmed severe splenomegaly. Cytologic examination of a bone-marrow core and histologic examination of spleen and liver biopsy samples revealed neoplastic small lymphocytes. Immunohistochemical staining of liver and spleen samples with the use of leukocyte-specific monoclonal antibodies showed that the neoplastic lymphocytes were immunoreactive to T-lymphocyte CD3 receptor and immunonegative to B-lymphocyte CD79a receptor. The morphology and distribution of neoplastic T-lymphocytes within the spleen, liver, peripheral blood, and bone marrow was most consistent with chronic T-lymphocytic leukemia. Treatment with chlorambucil and prednisone effectively decreased the lymphocyte count, but was associated with thrombocytopenia, which resolved after chlorambucil treatment was temporarily discontinued. Chemotherapy was resumed with a single dose of L-asparaginase, followed by a lower dosage of chlorambucil and continued prednisone. Two years after initial diagnosis, the hyena developed a hemoabdomen and was euthanized. Neoplastic T-lymphocytes were present in spleen, liver, visceral and peripheral lymph nodes, lungs, heart, kidney, adrenal glands, mesentery, intestines, pancreas, brain, and bone marrow.     

Hypercalcaemia associated with chronic lymphocytic leukaemia in a Giant Schnauzer.

A 7-year-old male Giant Schnauzer was referred with a history of severe vomiting, lethargy, weight loss, polydipsia and polyuria. Detailed investigations revealed leucocytosis with a marked lymphocytosis, mild non-regenerative anaemia, thrombocytopenia, hypercalcaemia and azotaemia. Circulating lymphocytes were small and well-differentiated, and the same lymphoid population was present in bone marrow. Chronic lymphocyctic leukaemia with associated paraneoplastic hypercalcaemia was diagnosed. Immunohistochemical staining of a bone marrow biopsy revealed a neoplastic B-cell line expressing CD79. The dog responded to therapy with prednisolone and chlorambucil for a period of 8 months.     

Polyostotic lymphoma with multiple pathological fractures in a six-month-old cat

A 6-month-old female neutered domestic shorthair cat was examined for pain and swelling of the distal limbs. Swelling and malalignment of both carpi, dorsiflexion of the distal metatarsals and a mild, multicentric lymphadenopathy were detected on examination. Screening blood tests revealed a biclonal gammopathy, hypercalcemia and atypical leukocytes. Survey radiographs revealed lysis and proliferative changes within the physes. Multiple pathological physeal fractures were present, including the distal radii, metacarpal and metatarsal bones. No treatment was attempted and the patient was euthanased. Histopathology revealed infiltration by monomorphic round cells within the liver, spleen, kidney and bone marrow. Immunohistochemistry revealed strong reactivity to CD20. Clonality assays revealed clonal results for the B-cell loci, consistent with B-cell lymphoma. To the authors' knowledge this is the first report of polyostotic lymphoma with multiple pathological fractures in a cat. The predominantly distal distribution of osseous lesions is rarely reported in dogs and humans.     

Canine intravascular lymphoma with overt leukemia

A 6-year-old spayed Labrador Retriever Mix dog was evaluated for a 2-week history of progressive generalized weakness and reluctance to stand. Physical examination revealed severe weakness with obtunded mentation, head tilt, bilateral nystagmus, and decreased vision. CBC findings included mild nonregenerative anemia, marked thrombocytopenia, and a few atypical mononuclear cells on the blood film. The cells were 15-30 μm in diameter and had round to oval to reniform centrally placed nuclei with stippled chromatin, prominent nucleoli, and abundant basophilic cytoplasm with numerous discrete vacuoles and, occasionally, small azurophilic granules. Similar cells were found in bone marrow. On histologic examination of tissues collected at necropsy, neoplastic cells were detected in bone marrow, hepatic sinusoids, cerebral and meningeal vessels, and in capillaries of the heart, renal interstitium, small intestinal submucosa, and muscularis, and alveolar septa. A small discrete mass in the right atrium consisted of similar neoplastic cells, and the spleen was diffusely infiltrated. Tissue distribution was suggestive of intravascular lymphoma. Neoplastic cells in tissue sections were immunoreactive for vimentin, CD18, CD45, and granzyme B and lacked immunoreactivity for cytokeratin. Neoplastic cells on bone marrow aspirate smears and blood films lacked immunoreactivity for CD3, CD79a, CD1c, CD11b, CD11c, CD11d, and E-cadherin. In the absence of immunophenotypic evidence for the neoplastic cells being derived from B-cell, T-cell, or histocytic/dendritic lineages and the lack of clonal antigen receptor gene rearrangement(s), along with positive immunoreactivity for granzyme B, a tumor of NK cells was considered likely. Based on current knowledge, this is the first report of canine intravascular lymphoma, of probable NK cell origin, with peripheral blood involvement.     

Cutaneous lymphoplasmacytic lymphoma with systemic metastasis in a cat

A lymphoplasmacytic lymphoma was diagnosed in a 12- year-old domestic cat that had a primary cutaneous mass involving the stomach, liver, kidneys, heart, abdominal wall, diaphragm, bone marrow and several lymph nodes. Histopathologically, the most characteristic feature of this tumor was the heterogeneity of cell components, such as small lymphocytes, well-differentiated plasma cells and plasmacytoid transformed lymphocytes. Amyloid was deposited in the skin, stomach, and several lymph nodes. Immunohistochemically, neoplastic small lymphocytes were positive for CD20, and well-differentiated plasma cells and plasmacytoid transformed lymphocytes were positive for λ-Ig light chains and MUM1/IRF-4. These results emphasize the importance of lymphoplasmacytic lymphoma as a differential diagnosis of extramedullary cutaneous plasmacytoma in cats.     

Engraftment of canine peripheral blood lymphocytes into nonobese diabetic-severe combined immune deficient IL-2R common gamma chain null mice

To study the canine immune system we generated a mouse model engrafted with canine lymphocytes using NOD SCID IL2R common gamma chain ?/? (NSG) mice as recipients (Ca-PBL-SCID). Engraftment of canine peripheral blood lymphocytes (PBLs) was determined post-injection with 10⁷ peripheral blood mononuclear cells (PBMCs) into irradiated NSG mice using flow cytometry and fluorescently labeled antibodies specific to canine helper T cells (CD45⁺ CD4⁺), cytotoxic lymphocytes (CD45⁺ CD8⁺), regulatory T cells (CD45⁺ CD4⁺ Foxp3⁺), and B cells (CD45⁺ Ig⁺ CD21_lo). Canine CD45⁺ lymphocytes were detectable as early as day 1 in the peritoneal cavity, and beginning at 9 days in the blood, bone marrow, and spleen. CD4⁺ T cells, of which Foxp-3⁺ CD25_hi cells constituted a minor percentage, were the predominant lymphocyte population at 9 days post engraftment contrasting with increasing proportions of CD8⁺ CTL's and Ig⁺ B cells beginning at 16 days. Canine immunoglobulin was initially detected in the serum of Ca-PBL-SCID mice at 9 days post-engraftment and peaked in concentration at day 36. From day 28 to 52 post-engraftment 30% of the Ca-PBL-SCID mice became markedly anemic and thrombocytopenic, yet gross and histopathologic examination of bone marrow, kidneys, spleen, liver, and intestine revealed no obvious lesions. Blood smear evaluation revealed agglutination of mature red blood cells, reticulocytes and a regenerative anemia. These findings demonstrate that NSG mice are capable of engraftment of canine PBLs yet develop graft versus host disease similar to Hu-PBL-SCID mice.     

Visceral leishmaniasis in a dog: clinical, hematological and pathological observations.

Visceral leishmaniasis was diagnosed in a dog that had been living with his owners in Spain for two years. Clinical diagnosis was somewhat delayed as the disease is largely unknown to Canada and was manifested by a nonresponsive anemia which was not easily explained on peripheral blood evaluation alone, and concomitant interstitial nephritis. On post mortem examination splenomegaly was the main gross pathological finding. Light microscopic examination of bone marrow aspirates and subsequent electron microscopic examination of splenic and hepatic tissues revealed numerous Leishman-Donovan bodies in cells of the reticuloendothelial system. Parasitized reticuloendothelial cells were seen singly or forming granulomata. These latter did not contain giant cells and were confined mainly to the liver and spleen, being sparse and single in the first but extremely numerous and coalescing in the latter. Accumulation of intrafollicular hyaline material was seen in a small number of splenic follicles. Leishman-Donovan bodies on electron microscopic examination had a trilaminar periplast, a large round nucleus with heavy blocks of marginated chromatin and two nucleoli, a short flagellum and a kinetoplast. Lymph nodes and bone marrow had numerous parasitized macrophages but no granulomata. Leishman-Donovan bodies were not detected in the lungs and kidneys both of which exhibited a chronic intersitital reaction. The comparative hematological profile as well as the importance of bone marrow and electron microscopic examinations of the spleen and liver in diagnosis are discussed. The potential public health hazard of leishmaniasis to North America and particularly to Canada is considered.     

Spontaneous Malignant T Cell Lymphoma in a Young Male Common Marmoset (Callithrix jacchus)

We histopathologically and immunohistochemically investigated a case of malignant lymphoma that spontaneously developed in a male common marmoset at two years of age. Beginning at two years four months of age, the animal had an enlargement of the submandibular and inguinal lymph nodes, small subcutaneous nodules near the right breast and an approximately fivefold increase in peripheral lymphocyte count compared with the previous examination value. The postmortem findings at two years eight months of age showed lymphadenopathy with enlargement of the thymus and spleen. Small- to intermediate-sized neoplastic lymphocytes had diffusely proliferated in the enlarged nodes. The neoplastic cells were pleomorphic and had irregularly shaped nuclei. The nuclear chromatin staining revealed hyperchromatism in the small-sized cells, and the intermediate-sized cells exhibited vesicular staining. An immunohistochemical examination indicated that the neoplastic lymphocytes were positive for CD3 and negative for CD20, thus suggesting that they had originated from T cells. In addition, the proliferation of high endothelial venules and reactive epithelioid histiocytes was observed. Scattered tingible body-laden macrophages were infrequently detected. Neoplastic lymphocytes were also observed in the thymus, spleen, heart, lungs, liver, kidneys, adrenal glands and femoral and sternal bone marrow. This malignant lymphoma in a young male common marmoset was considered to fit the category of “peripheral T-cell lymphoma, not otherwise specified (PTCL-NOS)” according to the new WHO system of classification.     

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.     

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.     

Erythrophagocytic low‐grade extranodal T‐cell lymphoma in a cat

Abstract: A 13‐year‐old male castrated domestic shorthair cat was presented to the referring veterinarian with a 2‐month history of weight loss and lethargy. Splenomegaly, hepatomegaly, nonregenerative anemia, neutropenia, and hyperbilirubinemia were noted. Results of testing for feline immunodeficiency virus, feline leukemia virus, Toxoplasma gondii, and Mycoplasma sp. were negative. On cytologic examination of aspirates from the enlarged spleen and liver, a population of erythrophagocytic round cells was observed. Splenectomy and a liver biopsy were done which revealed a population of CD3+/CD79a– erythrophagocytic mononuclear round cells localized in the hepatic and splenic sinusoids. T‐cell PARR (PCR for antigen receptor gene rearrangements) analysis of bone marrow and spleen demonstrated a single band indicative of a clonal proliferation of T cells. Based on the marked splenomegaly, sinusoidal infiltration, lack of lymphadenopathy, and results of cytology, PARR, and immunophenotyping, a diagnosis of low‐grade extranodal T‐cell lymphoma was made. The cat was treated with chlorambucil and prednisolone; clinical and laboratory abnormalities resolved and the cat has remained clinically normal for 2.5 years. To our knowledge, this report documents the first case of an erythrophagocytic T‐cell lymphoma in a cat. The clinicopathologic findings were suggestive of hepatosplenic T‐cell lymphoma, a neoplasm described previously only in humans and dogs.     

Systemic AL amyloidosis associated with multiple myeloma in a horse

AL amyloidosis is the most common type of systemic amyloidosis in humans, and it is frequently associated with multiple myeloma. But, AL amyloidosis is very rare in domestic animals. A 16-year-old Quarter horse gelding was diagnosed with systemic AL amyloidosis associated with multiple myeloma. Clinical problems were rapid weight loss, muscle atrophy, soft unformed stool, and ventral edema. Grossly, diffuse gastrointestinal hemorrhage, markedly thickened jejunal mucosa, and splenomegaly were present. Microscopically, diffuse severe amyloid deposits were present in the lamina propria of glandular stomach, duodenum, and jejunum. Much of the spleen and sternal bone marrow was replaced by neoplastic round cells, and multiple foci of amyloid were also present in the spleen and bone marrow. Electron microscopy revealed the neoplastic round cells to be of plasma cell origin, and the amyloid showed a strongly positive immunoreactivity with polyclonal anti-human immunoglobin lambda light-chain antisera. To our knowledge, this is the second report describing systemic AL amyloidosis in domestic animals-associated plasma cell neoplasia and the first associated with multiple myeloma, as is common in humans.     

Spontaneous Malignant T-cell Lymphoma in a Young Adult Crl:CD (SD) Rat

We investigated a case of spontaneous malignant T-cell lymphoma observed in a 19-week-old male Crl:CD (SD) rat. The rat showed paralysis beginning 1 week before euthanasia. Hematological examination revealed marked lymphocytosis without distinct atypia. Macroscopically, hepatosplenomegaly and partial atrophy of the thoracic spinal cord were observed. Microscopically, neoplastic cells infiltrated into the liver, splenic red pulp, bone marrow and epidural space of the thoracic spinal cord, while no neoplastic cells were observed in the thymus and lymph nodes. Moreover, the spinal cord showed focal degeneration due to compression by marked infiltration of neoplastic cells in the subdural space. The neoplastic cells were generally small-sized round cells that had a round nucleus with/without a single nucleolus and scanty cytoplasm. Immunohistochemically, the neoplastic cells were positive for CD3 and CD8 and negative for CD79α. Judging from these results, the present tumor in this young adult rat was diagnosed as malignant T-cell lymphoma.     

MYELOID NEOPLASIA IN A DOG

A 4-year-old Scotch Collie bitch was presented for examination because of hyperthermia and anaemia. Haematological examination and bone marrow biopsy led to a diagnosis of myeloid neoplasia. At autopsy there was slight enlargement of the liver, spleen and some lymph nodes. Microscopic examination revealed extensive infiltration of these tissues by neoplastic myeloid cells.     

Evaluation of monoclonal antibodies for identification of subpopulations of myeloid cells in bone marrow obtained from dogs

OBJECTIVE: To evaluate monoclonal antibodies that may be useful for immunophenotyping myeloid cells in bone marrow of dogs. SAMPLE POPULATION: Bone marrow specimens obtained from 5 dogs. DESIGN: Specimens were labeled with monoclonal antibodies that detected CD18, major histocompatability antigen class-II (MHC class-II), CD14, and Thy-1. Cells labeled with each of the antibodies were isolated by use of a fluorescence-activated cell sorter. Differential cell counts of sorted cells were used to determine cells that were labeled by each of the various antibodies. RESULTS: Myeloid cells labeled with anti-CD18 antibody included granulocytes, lymphocytes, and monocytes-macrophages. Immature and mature granulocytes were labeled. Lymphocytes, monocytes-macrophages, and eosinophils were labeled with anti-Thy-1 antibody. Cells labeled with anti-MHC-class II antibody included approximately 9% of bone marrow cells, which consisted almost exclusively of lymphocytes and monocytes-macrophages. Approximately 4% of bone marrow cells were labeled with anti-CD14 antibody, with > 90% of sorted cells being monocytes-macrophages. CONCLUSIONS AND CLINICAL RELEVANCE: Four monoclonal antibodies for use in detecting subpopulations of canine bone marrow cells were evaluated. These antibodies should be useful in differentiating the origin of leukemic cells in dogs.     

Histiocytic sarcoma of macrophage origin in a cat: case report with a literature review of feline histiocytic malignancies and comparison with canine hemophagocytic histiocytic sarcoma

Mild nonregenerative anemia was detected in a 9-year-old neutered male domestic shorthair cat during a routine examination. Bone marrow core biopsy revealed erythroid hyperplasia; however, a specific cause was not identified. Over the next 8 months the anemia progressed, eventually becoming mildly regenerative, and moderate thrombocytopenia developed. On ultrasonographic examination, marked splenomegaly, mild hepatomegaly, and abdominal lymphadenopathy were found. Cytologic evaluation of splenic aspirates revealed increased numbers of mildly to moderately pleomorphic histiocytes that frequently had phagocytosed RBCs, leukocytes, and occasionally platelets. Histopathologic examination of the spleen and liver revealed effacement of splenic architecture by a histiocytic sarcoma (HS), and neoplastic histiocytes in hepatic sinusoids. A second bone marrow aspirate revealed neoplastic infiltration by similar cells. The histiocytes in all tissues were mildly to moderately pleomorphic and markedly erythrophagocytic. The immunophenotype of histiocytes in the spleen was CD1c(-)/CD11b(+)/CD18(+)/MHC-II(+), supporting a macrophage cell lineage. The clinical, pathologic, and immunophenotypic findings in this cat were similar to those in hemophagocytic HSs in dogs. To our knowledge, this is the first report of a HS of purported macrophage phenotype in a cat.     

Disseminated histiocytic sarcoma with peripheral blood involvement in a Bernese Mountain dog

Abstract: A 6‐year‐old Bernese Mountain dog was presented with a history of lethargy and weight loss of 2 weeks duration. On physical examination the dog had pale mucous membranes and tachypnea. Ultrasound examination revealed hepatomegaly, splenomegaly, and mesenteric lymphadenomegaly. Results of a CBC included marked normocytic normochromic nonregenerative anemia, marked thrombocytopenia, and moderate leukocytosis with mild neutrophilia and a large population of unclassified round cells (6.2 × 10³/μL). The unclassified cells occasionally were bi‐ or multinucleated and had variably abundant pale basophilic cytoplasm that contained multiple irregular clear vacuoles and occasionally erythrocytes. Fine needle aspirate specimens of the mesenteric lymph nodes and spleen were composed of a population of round pleomorphic cells with the same features as the circulating cells. On flow cytometric analysis of peripheral blood, the unclassified cells expressed CD18, CD45, CD11c, CD1c, and CD14; immunocytochemical analysis of blood smears also indicated the cells were positive for CD1c, CD1a, and CD11c. The dog died a few hours after referral. The histologic interpretation of samples collected from spleen, liver, and lymph nodes was malignant neoplasia of histiocytic origin. Immunohistochemical staining yielded negative results for CD11d, a marker of red‐pulp macrophages, ruling out hemophagocytic histiocytic sarcoma. Based on clinical and pathologic findings, the final diagnosis was disseminated histiocytic sarcoma (DHS) with peripheral blood involvement. To our knowledge, DHS in a dog with evidence and immunophenotyping of neoplastic cells in peripheral blood has been reported only rarely.     

Myeloperoxidase-positive acute megakaryoblastic leukemia in a dog

A 16-month-old female spayed Labrador Retriever was referred to the University of Edinburgh for exercise intolerance, inappetence, and severe anemia. A CBC showed severe nonregenerative anemia and moderate numbers of atypical cells with morphologic features most consistent with megakaryoblastic origin. Similar cells were identified in a bone marrow aspirate and accounted for 23% of all nucleated cells. Atypical promegakaryocytes and megakaryocytes were also noted. Myelodysplastic syndrome affecting the megakaryocytic lineage was suspected. Cytologic examination of a fine-needle aspirate of the spleen revealed rare megakaryoblasts similar to those in blood and bone marrow. At necropsy, the bone marrow consisted of atypical megakaryoblasts and megakaryocytes that were also infiltrating spleen, liver, lymph nodes, renal perihilar tissue, and visceral adipose tissue, consistent with acute megakaryoblastic leukemia. Immunohistochemical analysis of splenic sections confirmed megakaryoblastic origin (immunoreactive for CD61 and von Willebrand factor). Some leukemic cells were also immunoreactive for myeloperoxidase (MPO). This aberrant immunophenotype suggested both megakaryocytic and granulocytic/monocytic differentiation of the leukemic cells. To our knowledge, this is the first report of MPO-positive acute megakaryoblastic leukemia in a dog.