Cutaneous melanocytomas in 10 young cattle.

Ten melanocytomas from 10 cattle were diagnosed by histopathologic examination of biopsy specimens submitted to the Veterinary Medical Diagnostic Laboratory, University of Missouri, between 1 January 1986 and 31 December 1993. One tumor was congenital; the others were first noticed between 2 months and 2 years of age (means = 9.9 months). Six tumors occurred in purebred (3) or crossbred (3) Angus cattle; one tumor each occurred in a Holstein, a Shorthorn, a Simmental, and a beef calf of unrecorded breed or coat color. Five calves were female, and five were male. Five tumors occurred in truncal dermis or subcutis (three in abdominal skin), four occurred on a limb, and one occurred on the jaw. Tumors varied in histologic appearance, but all were pigmented and all had few mitotic figures. Outcome was known for 8/10 cattle. In four cattle followed for at least 1 year, the tumor did not recur after surgical excision. Another heifer had residual gray tissue at the tumor site after surgery but remained in the herd without regrowth of the tumor 30 months after excision. Three other calves were slaughtered within 6 months of excision without apparent recurrence of the tumor.