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

Abstract

Background Cutaneous epitheliotropic T-cell lymphoma is a malignant tumour of the skin already reported in humans, dogs, cats, horses, and other species, but not previously in donkeys. The standard diagnosis is based on clinical, morphological and immunophenotypic data. Differentiation of malignant versus benign proliferation of lymphocytes is crucial; in ambiguous cases T-cell receptor gamma (TRG) molecular clonality should be tested. In the present paper, we report a case of mycosis fungoides diagnosed in a donkey whose diagnosis was based on clinical, histological and immunohistochemical aspects and a positive TRG clonality test. Case presentation A twenty-five-year-old donkey gelding was referred with a mildly pruritic, generalised and severe exfoliative dermatosis. Otherwise, the animal was clinically healthy, though mildly underweight. Dermatological examination revealed severe generalised alopecic and exfoliative dermatitis, occasionally eroded, with high number of large, thin, greyish scales. All mucocutaneous junctions except the hoofs were affected. Ectoparasites and dermatophytes were ruled out. The complete blood count and blood smear evaluation revealed mild normocytic normochromic anemia. The biochemistry panel showed mild hyperproteinemia with albumin within the normal range. Protein electrophoresis showed moderate polyclonal hypergammaglobulinemia. Histological findings were characterised by interface dermatitis with massive exocytosis in the epidermis of a homogenous population of lymphoid cells showing atypia. Clusters of neoplastic cells were present within the epidermis forming Pautrier “microabscesses”. These findings are consistent with cutaneous epitheliotropic lymphoma. Immunohistochemical staining revealed uniform labelling of the neoplastic cells for CD3, and lack of expression of CD20 (a B cell lineage associated marker). Molecular clonality PCR (PARR) was performed using equine TRG primers; this revealed a clonal rearrangement in a heavy polyclonal background. Transmission electronic microscopy showed multiple lymphocytes with convoluted or cerebriform nuclei. Conclusions This case report provides the first evidence of clinical, histopathological, immunophenotypic features, electron microscopy findings and molecular analysis of a cutaneous epitheliotropic T-cell lymphoma (mycosis fungoides) in a donkey. Our observations suggest that cutaneous T-cell lymphoma should be included in the differential diagnoses of exfoliative dermatitis, even those progressing in a chronic pattern and/or with few or no pruritus.

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

“…Although the use of PARR has been described as an adjunct diagnostic test for lymphoma in horses and a donkey, the methods have not been described in detail in the literature. 1,5,8…”

“…Although the use of PARR has been described as an adjunct diagnostic test for lymphoma in horses and a donkey, the methods have not been described in detail in the literature. 1,5,8 An 8-y-old male Quarter Horse developed anorexia of acute onset. A few hours later, the horse ran uncontrollably into a fence and was placed in a stall overnight for observation.…”

“…4,6,15 The PARR assay is routinely used as an adjunct diagnostic technique in canine and feline lymphoma, and 3 reports describe its application in equine lymphoma and leukemia, although the methods were not provided. 1,5,8 Here we describe the use of the PARR assay for diagnostic confirmation of an equine lymphoma with detailed methods and utilized primers. Because the assay is newly developed, diagnostic sensitivity and specificity have not yet been determined.…”