Carcinoma de células escamosas metastático em um equino

Background: Squamous cell carcinoma is a relatively commum cutaneous neoplasia in a horse, originated mainly in external genitalia, periocular region, especially, eyelids and oral cavitity. Squamous cell carcinoma metastasis was considered rare. Depigmentation, ultraviolet light exposure and actinic acantosis were considered etiopathologic factors. The squamous cell carcinoma rarely metastasizing however causes severely local invasion. The diagnosis confirmation just was done for histopathological and citopathological exams. The following report outlines clinical and pathological findings of a case of a metastatic squamous cell carcinoma to multiple sites in a horse revealed after anatomopathological exam.
Case: The case consisted of a 10-month old Appaloosa x Mangalarga horse whose owner’s main complaint was a multiple ulcerative tumor in the nasal region of the animal. The horse presented depigmented libs, narines, prepuce and peniane tegument. The lesion beginning at 12 months and the horse presented sneezing and intermittent epistaxis of the right narine and moderated sialorheia. During clinical evaluation, the animal presented discrete dispneia e severe emaciation. The tumor invaded into deep inner nasal cavity, causing partial stenosis of the nasal passage of the left nasal cavity. How- ever, stenosis and bleeding is not allowed to specify the compromised extension. The location and extent of these injuries hindered breathing and chew food. Due to the debilitating general condition of the animal and prior consent of the owner, we opted for euthanasia and necropsy. The primary mass was 15x3x5 cm in diameter, ulcerated, irregular surface on the left medial asa of the narine. The tumor infiltrate to nasoincisive incisures, lateral of left lips and narine. During necropsy observed masses the ventral subcutaneous cervical region, salivar glands, perianal region and lungs. Histological examina- tion of formalin-fixed tissue specimen revealed lobules and nests of neoplastic epithelial cells and keratin pearls. The same infiltration neoplastic type was observed on the salivary glands, perianal region and lung nodules.
Discussion: The diagnostic confirmation of the present case was based on its clinical, epidemiological and morphological characteristics, particularly histopathological findings. On the present case, the necropsy was fundamental to diagnose and metastasis observation. It may raise anywhere in the body with a multifactorial etiology, and, the exposure to ultraviolet light and lack of nasal skin pigmentation are considered the main predisposing factors. The horse observed in this study is Appaloosa x Mangalarga, with 10 months years of age, set up outdoors and exposed to constant solar radiation. Appaloo- sas, American Paint Horses, Thoroughbreds, and Quarter Horses are reported in literature as being the most predisposed ones. The progressive sneezing signs with hemoptysis were associated to tumor ulcer in the nasoincisive incisures. The sialorheia was due neoplastic invasion into submandibular and parotids salivary glands, confirmed in the histopathological exam. The squamous cell carcinoma rarely metastasizing however in the present case observed multiples sites and organs with the neoplasm invasion, like salivary gland, subcutaneous and lung. The main microscopic findings and characteristic of the neoplasm were keratin concentric deposition in the central of neoplastic keratinocytes (keratin whorls) and high anaplastic cells.

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