Cutaneous epitheliotropic T-cell lymphoma in a donkey - a case report

Multicentric lymphoma in a donkey with intestinal and bone marrow involvement

BACKGROUND

Lymphoma is a common neoplasm in horses but is reported much less commonly in donkeys. In this case report, we describe the macroscopic, microscopic and immunohistochemical features of a multicentric lymphoma with intestinal and bone marrow involvement.

CASE PRESENTATION

A geriatric female donkey with history of chronic lameness was found dead. Post-mortem examination revealed advanced emaciation, periodontal disease, left front foot laminitis and multiple, soft, white to yellow tan intestinal transmural masses, up to 12 cm in diameter. Cytology suggested a round cell intestinal neoplasm. The femur of the left hint limb was double the size of the normal contralateral, with suspected neoplastic infiltration and replacement of bone marrow and bone. Histologically we diagnosed a lymphoma in the intestine and left femur. Immunohistochemically, the neoplastic cells showed CD3 immunolabelling, supporting a diagnosis of a multicentric T-cell lymphoma.

CONCLUSIONS

To the authors' knowledge, this is the first time multicentric lymphoma is diagnosed in donkeys. Further studies of the genetic background, clinical, laboratory, histopathologic, and immunohistochemical, as well as the pathogenesis of lymphoma, is needed to better understand the uniquely low frequency of this neoplasm in donkeys.

Case report: Identification of the tropical rat mite (Ornithonyssus bacoti) on a domestic donkey in France

A 25-year-old donkey was referred for a generalized, pruritic and severe exfoliative dermatitis that had been evolving for several years, with deterioration in the last few months. Close examination of the skin surface revealed numerous small, dark, mobile elements identified as Ornithonyssus bacoti confirmed by DNA sequencing. The severity, type and topography of the lesions called for complementary examinations, leading to a second diagnosis of cutaneous epitheliotropic T-cell lymphoma. The lack of clinical improvement after antiparasitic therapy despite parasite clearance, suggests opportunistic behavior of Ornithonyssus bacoti. To the best of our knowledge, this is the first report of the presence of a tropical rat mite on a donkey, thus expanding the known host spectrum of this zoonotic parasite. Further potential questions concern the implication of this new host as a possible source of human contamination.

T-cell-rich, large B-cell lymphoma in the brain of a horse

T-cell-rich, large B-cell lymphoma (TCRLBCL) is the most commonly diagnosed type of lymphoma in horses. Here we describe the clinical signs, neuropathology, immunohistochemistry (IHC), and PCR for antigen receptor rearrangement (PARR) analysis results of a TCRLBCL in the brain of an 8-y-old male Quarter Horse that was euthanized after acute anorexia, tremors, head pressing, falling, blindness, incoordination, and seizures. Autopsy revealed a firm, smooth, pale-yellow mass that expanded both lateral ventricles and the adjacent subcortical white matter. Histologically, the mass consisted of a densely cellular neoplasm composed of large, CD79+ neoplastic B-lymphocytes admixed with sheets of small, CD3+ reactive T-lymphocytes, Iba1+ histiocytes, MUM1+ plasma cells, and rare eosinophils supported by a fine fibrovascular stroma. Formalin-fixed, paraffin-embedded tissue scrolls were retrieved and subjected to PARR analysis, which revealed a clonal reaction in the immunoglobulin gene and a polyclonal reaction for the T-lymphocyte receptor gene, consistent with a neoplastic B-lymphocyte and reactive T-lymphocyte proliferation. The diagnosis of TCRLBCL was suspected histologically and confirmed based on IHC and PARR analysis.