Mastocytosis in the skin in dogs: A multicentric case series.

Canine cutaneous mastocytosis (CM) is rare in contrast to canine mast cell tumours. In humans, CM commonly affects children and is usually indolent with possible spontaneous resolution. Systemic mastocytosis (SM) with bone marrow involvement typically affects adults, can have a poor outcome, and often includes skin lesions. 'Mastocytosis in the skin' (MIS) is the preferred term of skin lesions, if bone marrow evaluations are not available, which is often the cases in dogs. In human SM and CM, KIT mutations are often detected. The veterinary literature suggests clinical resemblances between human and canine MIS, but data is limited, and KIT mutations are rarely assessed. This retrospective study describes clinicopathological findings, treatment and outcome of 11 dogs with suspected MIS. Dogs with multiple mast cell tumours were excluded. Histopathology reports (n = 5) or slides (n = 6) were reviewed. KIT mutation analysis including exons 8, 9, 11, 14 and 17 were analysed in eight dogs. Median age at diagnosis was 4 years (range, 1-12). Typical clinical signs included multifocal to generalised nodules and papules. Histologically, skin lesions were characterised by dermal infiltration of well-differentiated mast cells. KIT mutations were detected in 3/8 dogs (exon 9: n = 2; exon 11: n = 1). One dog had mastocytaemia suggesting possible SM. Glucocorticoids were mostly successful with lesion improvement in all treated dogs (n = 8). This cohort highlights resemblances between human and canine MIS. Further studies are required to confirm these findings and establish diagnostic criteria for CM and MIS associated with SM in dogs.

Características clínicas, histopatológicas e imuno-histoquímicas do mastocitoma cutâneo equino: relato de caso / Clinical, histopathological and immunohistochemical chacteristics ofequine cutaneous mastocytoma: case report

Uma égua puro sangue árabe, com 3 anos de idade, pertencente ao rebanho experimental da FMVZ-USP apresentou lesões tumorais cutâneas nos membros pélvicos direito e esquerdo com aproximadamente um ano de evolução. Notou-se nova formação cutânea com crescimento rápido na região do pescoço, e desde então, as lesões dos membros ganharam características inflamatórias. Foi realizada punção aspirativa da lesão do pescoço para análise citológica, em que se identificou infiltrado eosinofílico. Optou-se pelo início de tratamento conservativo com três infiltrações intralesionais consecutivas com corticoesteroide. A partir da falta de sucesso das infiltrações foram realizadas as excisões cirúrgicas totais dos nódulos do pescoço, membro pélvico direito e esquerdo. Todos os materiais obtidos dos procedimentos cirúrgicos foram enviados para avaliação histopatológica e imuno-histoquímica, nas quais se confirmou o diagnóstico de mastocitoma cutâneo. O animal recebeu alta após a cicatrização das feridas cirúrgicas e remissão dos sinais, e não demonstrou recidivas ou outras complicações advindas das lesões tumorais. Algumas neoplasias cutâneas são bem descritas e de comum ocorrência na espécie equina, como o sarcoide, melanoma, papiloma e tumor de células escamosas. Já o mastocitoma cutâneo consiste em neoplasia cutânea rara nessa espécie. Segundo a literatura, não parece existir uma predileção racial para o aparecimento deste tumor, entretanto, alguns autores citam o acometimento maior nos animais Puro Sangue Árabe. Para o estabelecimento do diagnóstico definitivo é importante a associação dos exames físico, histopatológico e imuno-histoquímico e, apesar desta neoplasia ser de raro aparecimento nos equinos, deve ser sempre considerada como diagnóstico diferencial.

A 3 year-old mare, Arab, that belongs to the experimental herd of FMVZ-USP presented cutaneous tumor lesions on right and left posterior limb with approximately one year of evolution. A new formation with rapid growth was observed on the neck region, and since then, the limbs lesion gained inflammatory characteristics. Aspirative punction was performed on the neck formation in order to submit the sample to cytological analyses, in which eosinophilic infiltrate was identified. At this point, a conservative approach was chosen with three consecutive corticoid infiltrations. With lack of success of infiltrative therapy, neck, right and left posterior limbs lesions were surgically removed. The materials obtained from surgical procedures were sent to histophatological and immunohistrochemical evaluation that confirmed cutaneous mastocytoma diagnosis. The mare was discharged after all surgical wound were healed and after full remission of clinical signs, and did not show relapses or any other complication from tumor lesions. Some cutaneous tumors are well described and commonly occur in horses, such as sarcoids, melanoma, papilloma and squamous cell carcinoma. Cutaneous mastocytoma is considered a rare cutaneous tumor in this species. According to literature, equine mastocytoma do not have breed predilection, however, some authors mention a greater involvement in Purebreed Arabian horses. In order to establish a definitive diagnosis, it is important to associate physical exams to histophatological an immunohistochemical evaluation and, even though rare in horses, this neoplasm must be considered as a differential diagnosis.