Equine Cutaneous Lymphoma: A Case Report

Abstract

Résumé— Les commémoratifs, les symptômes, l'histologie et la réponse au traitement d'un cheval de 15 ans atteint de lymphome cutané sont décrits. La jument présente de multiples nodules cutanés depuis 11 ans. Un diagnostic de lymphome cutané est poséà l'examen histologique de biopsies réalisées 2 fois à 4 ans d'intervalle. Des marquages immunihistochimiques identifient ces cellules comme appartenant à la lignée T. Ceci est la première description du marquage immunophénotypique d'un lymphome cutané chez le cheval. La jument a été traitée par des glucorticoïdes intralésionnels et des progestagènes oraux ce qui a entrainé une régression complète des nodules. Resumen— Describimos la historia clinica y los hallazgos clinicos e histológicos de un caballo de 15 años con un linfoma cutáneo. La yegua tenia una historia clinica de multiples nédules cutáneos en los últimos 11 años. Se diagnosticó un linfoma cutáneo mediante estudio histológico de dos biosias tomadas con unos cuatro años de separación. Tinciones inmunohistoquimicas ulteriores identificaron la linea celular de ünfocitos T. Este es el primer estudio que caracteriza el linfoma equino a nivel inmunofenotipico. La yegua fue tratada con glucocorticoides intralesionales y progestágenos orales, lo que resultó en curación total de los nódulos. Abstract— The history, clinical and histological features and response to treatment of a 15‐year‐old horse with cutaneous lymphoma are described. The mare had an 11 year history of multiple cutaneous nodules. A diagnosis of cutaneous lymphoma was made on histological examination of biopsy material taken on two separate occasions some 4 years apart. Subsequent immunohistochemical staining identified the cell lineage as T‐lymphocytes. This is the first report of immunophenotypic characterisation of cutaneous lymphoma in the horse. The horse was treated with intralesional glucocorticoids and oral progestins, and complete resolution of the nodules resulted.

Immunohistochemical Characterization of Estrogen and Progesterone Receptors in Lymphoma of Horses

“…All of the splenic and subcutaneous tumors of the horses in this study contained neoplastic populations of B cells. Previous reports and clinical observations have indicated that the subcutaneous form of lymphoma has a waxing and waning nature that often occurs with alterations in hormonal activity 30,32 and that some equine cutaneous and subcutaneous lymphomas may regress upon administration of progestins 31,32 . Although the internal location of splenic lymphoma does not lend itself to simple observation, the higher rate of PR expression in these tumors warrants consideration of similar responsiveness to hormonal influences.…”

“…Progesterone and the synthetic progestins medrox‐yprogesterone and norgestrol also exert cytostatic and cytotoxic effects against lymphoblastic and nonlym‐phoblastic leukemia and myeloma cell lines from human beings, although the exact mechanism of action of this inhibitory effect is unclear 39 . The fluctuation in subcutaneous T‐cell‐rich large B‐cell lymphomas in horses, presumably in response to fluctuations in hormonal activity, was observed in 2 horses in which tumors regressed after administration of a synthetic progestin 30–32 …”

“…There are clinical and anecdotal observations of neoplastic nodules in some horses with subcutaneous lymphoma that wax and wane in conjunction with hormonal events such as estrus, foaling, and lactation. In one reported case of equine cutaneous lymphoma, intralesional glucocorticoids and oral administration of progestins resulted in complete remission of the nodules 31 . In another report, regression of subcutaneous lymphoma in a mare was associated with administration of progesterone and removal of an ovarian granulosa‐theca cell tumor 32 .…”

Cutaneous lymphohistiocytic and multifocal lymphoma in an adult mare

“…However, the same is not true regarding the age or the breed of the affected horses, although cutaneous lymphoma more often occurs in adult to aged animals (Scott and Miller 2003). From a clinical and histopathological point of view, the primary cutaneous lymphoma in the horse is actually non-epitheliotropic and subcutaneous and only rarely epitheliotropic (Staempfli et al 1988, Littlewood et al 1995, Hübe et al 1997, Johnson et al 1998, Potter and Anez 1998, Epstein and Hodge 2005, de Brujin et al 2007). The latter form is expressed as multifocal to generalized exfoliative dermatitis and is accompanied or not by pruritus and sometimes by nodules and ulcerations, as it has been witnessed in other animal species (Scott and Miller 2003).…”

“…Peripheral blood haematology and serum biochemistry were normal in this mare, as it may happen in the majority of horses with the non-epitheliotropic phenotypic form of cutaneous lymphoma (Sheaham et al 1980, Littlewood et al 1995, Gerard et al 1998, Johnson 1998. Nevertheless, in equine lymphoma, and regardless of its clinical phenotype, anemia or erythrocytosis, neutropenia, lymphocytosis or leuke mia, hypoalbuminemia and/or hyperglobulinemia, either polyclonal or monoclonal, may be seen, more or less frequently (Meyer et al 2006).…”