A case of colic due to metastatic melanoma in a 23-year-old mare

Abstract

A 23-year-old grey Argentinian mare was presented with a history of chronic weight loss, anorexia, restlessness, pawing, rolling, frequent recumbency, straining to urinate, urinating frank blood and round and firm subcutaneous lumps on left neck and occiput. Clinical examination showed tachypnea, congested mucous membrane and capillary refill time greater than 2 seconds, bruises on different parts of the body, bilateral epiphora, sunken eyelids, and slight loss of skin turgor, body condition score of 3/5, depression and temperature of 38.9^oC. Abdominocentesis revealed frank blood while rectal palpation showed a large mass on the left quadrant. Haematology revealed increased packed cell volume (44 %), lymphopenia and neutrophilia. Serum biochemistry revealed hypercalcaemia, increased alanine aminotransferase, uremia, hyperproteinemia and hyperfibrinogenaemia. The horse was treated for colic and died 24 hours after the presentation. At post-mortem examination, the liver and spleen were remarkably enlarged and nodular with numerous surface melanomas. A large black firm nodular mass of about 7 kg was observed on the left kidney. Diagnosis of malignant melanoma was made. In conclusion, this case demonstrates the malignant behaviour of equine melanomas hence early detection and prompt treatment of small lumps before they proliferate is recommended.