Oral lymphoma with features of anaplastic large T‐cell lymphoma treated as an erosive and ulcerative stomatitis in a pony horse

Lymphoma is the most common malignant haemolymphatic neoplasm in the horse, with a predominance of multicentric T‐cell‐rich large B‐cell lymphoma. Anaplastic large T‐cell lymphoma is a rare subtype of T‐cell lymphoma characterised by presence of atypical neoplastic lymphoid cells with kidney‐shaped or horseshoe‐shaped nuclei. This case report describes an unusual presentation of a lymphoma with morphological and immunohistological features of an anaplastic large T‐cell lymphoma with oral mucosal involvement in a horse that was originally presented with erosive to ulcerative stomatitis.