Melanoma in a Dairy Goat

Abstract

Background: Skin neoplasms in goats, albeit less frequent than in equines and cattle, are no less important, given that the presence of melanoma is worrisome due to its local and metastatic aggressiveness, which leads to death, especially in northeastern Brazil, where ultraviolet (UV) radiation levels are high, being an important factor the development of this neoplasia, especially in light-skinned animals. This report describes the clinical and pathological aspects, beyond the attempted surgical treatment a case of Saanen goat melanoma raised in Feira Nova, Pernambuco, Brazil.

Case: A 4-year-old pregnant Saanen goat was treated at the AGA/UFRPE. The animal presented blackened fetid masses located on the lower lip and ventral region of the jaw that had grown for two months. In addition to the tumor, a physical examination revealed altered submandibular and left prescapular lymph nodes. Local anesthesia and sedation were applied and both neoplasms were excised.  The goat was then medicated with anti-inflammatory and antibiotic drugs and discharged. However, 45 days later, the goat returned with multiple nodules similar in appearance to the previous one and in a severe clinical condition, characterized by pale mucous membranes, dehydration, enophthalmia, bilateral nasal serous secretion and enlargement of the lymph nodes mandibular, retro pharyngeal and right paratid, as well as slight respiratory snores in the ventral portion of lungs and productive cough. Due to the unfavorable prognosis, the animal was euthanized. Macroscopic findings revealed multiple nodular, infiltrative and blackened lesions on the tongue, lung, kidneys and liver, enlarged and blackened lymph nodes, and sagittal section of the cervical spine identified a dark spot on the seventh thoracic vertebra. In the histological evaluation of necrotic lesions present in the skin, lung, liver and kidneys was observed nodular infiltration of anaplastic cells was noted, with anisocytosis, anisocariosis, multiple nucleoli and intracytoplasmic granulation compatible with melanin and larger amelanotic cells compatible with cells high degree of malignancy. The bone marrow of the mandible and vertebrae, in turn, have melocytic and amelanocytic cell metástases.

Discussion: The animal’s region of origin is characterized by high incident solar radiation, which, allied to skin depigmentation in this breed, favor the formation of neoplasms. Clinical signs are multifactorial, depending on the lesion, and may be nonspecific, as in this case. Ninety percent of cases occurring in the region of the mouth are malignant. The initial tumoral mass was located in the lower lip, which corresponds to the second region of highest incidence reported in the literature. Despite the aggressive and metastatic characteristics of melanomas, surgical excision and/or cryosurgery are the only forms of treatment, with a poor to reserved prognosis, depending on the occurrence of locoregional lymph node metastasis. Early detection can be achieved by aspiration biopsy cytology, which may suggest neoplastic cells, or by imaging exams that reveal possible metastases and adjacent structures compromised by tumors. Necropsy of the animal revealed local infiltration of the tumors and metastatic dissemination, which may be attributed to the depth of the lesion and extracellular propagation through blood vessel lumina. The histological findings revealed dissemination of neoplastic cells and intracytoplasmic melanin granulation, which are compatible with melanoma. Melanocyte metastasis to lymph nodes and vital organs leads to systemic involvement, so early identification and surgical removal of blackened and ulcerated masses is crucial.