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+, CD79alpha-) 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.

Equine lymphoma

“…Other cytological abnormalities reported in the peripheral blood smear of leukaemic horses include Heinz bodies and Sézary cells (medium to large lymphocytes with ceribriform nuclei resembling a monocyte and scant cytoplasm) (Rollins et al 1991;Polkes et al 1999). Other blood dyscrasias observed when there is malignant infiltration of bone marrow include thrombocytopenia and pancytopenia (Reef et al 1984;Roccabianca et al 2002;Meyer et al 2006;Kelton et al 2008). Serum biochemical abnormalities commonly encountered include hyperfibrinogenaemia, hypoalbuminaemia and hyperglobulinaemia (Neufeld 1973;van den Hoven and Franken 1983;Mair et al 1985;Savage 1998;Meyer et al 2006;Munoz et al 2009).…”

Hematopoietic Neoplasias in Horses: Myeloproliferative and Lymphoproliferative Disorders

“…The tissues most often involved in the multicentric or generalized lymphoma are, in decreasing order of frequency: lymph nodes (including the palpable peripheral lymph nodes, although in most of the cases, the only enlargement is in internal lymph nodes), liver (causing metabolic derangements and obstructive icterus) [11, 61], spleen [11], intestine (inducing colic or malabsorption syndrome with diarrhea or both) [26, 47], kidney (with hematuria or chronic renal failure), lung (leading to a chronic cough and mediastinal fluid accumulation with pleural effusion) and bone marrow [32]. More rarely, tumors can invade the upper airways, causing respiratory obstructions and coughing, spinal cord [30], with spinal compression and neurological signs, including paraplegia and hemiplegia, central nervous system [50], heart [50, 54] causing arrhythmias and altered valvular function, and retrobulbar space, with exophthalmos.…”

“…Myelodysplasic disorders refer to cells that are not truly neoplastic, but there is a suspicion of neoplasia. Myelophthisic disorders refer to the replacement of normal bone marrow by neoplastic or inflammatory tissue, with a loss of the normal architecture of bone marrow, although this condition has been uncommonly reported in horses [1, 32]. A classification of the hematopoietic neoplasias in horses is presented in Fig.…”

Clinicopathologic Findings of Spontaneous Leukemia in 9 Pet African Hedgehogs (Atelerix Albiventris)

“…One of these cases had diffuse marrow necrosis, presumably from death of the tumor cells in marrow, since postmortem examination showed a leukemic pattern of distribution in extramedullary tissues with no obvious masses. Spontaneous bone marrow necrosis has been rarely described in acute leukemia in humans (22) and animals (23). In one case (case 7), a distinction between leukemia and lymphoma could not be made.…”