Prognosis after surgical excision of canine melanomas

One hundred and thirty-four dogs from which melanomas had been excised were studied until death or for at least 2 years after surgery. Seven of 49 (14%) intraoral and lip tumours and 52 of 85 (61%) skin tumours were histologically benign; in spite of this, three of seven (43%) "benign" oral and four of 52 (8%) "benign" skin lesions led to the eventual death of the host. Thirty eight of 42 (90%) dogs with a histologically malignant melanoma of the lip or oral cavity died because of the tumour but only 15 of 33 (45%) with malignant skin melanomas died. Six of 59 (10%) dogs with a tumour of mitotic index 2 or less died from the tumour 2 years after surgery compared to 19 of 26 (73%) dogs having a tumour with a mitotic index of 3 or more.