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Melanoma[edit]
Multiple nodules at the tail-base.
Small nodules at the lip commisure.Common sites for melanomaMelanoma results from abnormal proliferation and accumulation of melanocytes, pigmented cells within the dermis. Gray horses over 6-years-old are especially prone to developing melanoma.[23] The prevalence of melanoma in gray horses over 15-years-old[24] has been estimated at 80%.[18] One survey of Camargue-type horses found an overall population prevalence of 31.4%, with prevalence increasing to 67% in horses over 15-years-old.[25] Up to 66% of melanomas in gray horses are benign,[18] but melanotic tumors in horses with darker hair-coats may be more aggressive and are more often malignant.[26] One retrospective study of cases sent to a referral hospital reported a 14% prevalence of metastatic melanoma within the study population. However, the actual prevalence of metastatic melanoma may be lower due to infrequent submission of melanotic tumors for diagnosis.[27] Common sites for metastasis include lymph nodes, the liver, spleen, lung, skeletal muscle, blood vessels and parotid salivary gland.[27]
Clinical signs[edit]The most common sites for melanotic tumors are on the under-side of the tail near the base, on the prepuce, around the mouth or in the skin over the parotid gland (near the base of the ear).[23] Tumors will initially begin as single, small raised areas that may multiply or coalesce into multi-lobed masses (a process called melanomatosis) over time.[3] Horses under 2-years-old can be born with or acquire benign melanotic tumors (called melanocytomas), but these tumors are often located on the legs or trunk, not beneath the tail as in older animals.[28]
h4v6sY |
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提升卡
置顶卡
沉默卡
喧嚣卡
变色卡
显身卡
IP卡
狗仔卡
