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Conjunctival malignant melanoma in a horse
C.P. Moore1, B.K. Collins, L.L. Linton
1Department of Veterinary Medicine and Surgery, College of Veterinary Medicine, University of Missouri, Columbia, MO 65211, USA; Animal Eye Specialists, 360 Blue Round Rd, Waukesha, WI 53186, USA; Animal Eye Clinic, 4441 Granite Dr, Ste 101, Rocklin, CA 95677, USA; Animal Eye Care, 5603 W. Canal Drive, Kennewick, WA 99336, USA.
Abstract:
A case of malignant melanoma originating from the conjunctiva of a horse is reported. The tumor exhibited locally aggressive behavior as evidenced clinically by recurrence following two treatment episodes including surgical excision on each occasion and one application of cryotherapy. The orbit was subsequently exenterated and histologically malignant conjunctival melanoma was confirmed. Histopathologic features included variable pigmentation with amelanotic sites demonstrating marked cellular and nuclear pleomorphism with high numbers of mitotic figures. Cords of neoplastic cells invaded the sclera and cornea. Following exenteration, the horse exhibited no recurrence of the tumor for five years before being lost to follow-up. To our knowledge, this is the first report of primary malignant conjunctival melanoma in a horse.