Cutaneous angiomatosis in a young dog.

A 1-year-old, spayed, female, mixed-breed dog had two reddish-purple cutaneous lesions, one on the right dorsal antebrachium and the other on the right shoulder. The lesions consisted of approximately 13 x 3 cm and 15 x 10 cm, irregular, patchy regions of 0.5-3.0 cm, circular, sometimes raised, reddish-purple swellings resembling ecchymoses. The lesion on the antebrachium had been noticed since the dog was adopted at 6 months of age and appeared to have increased in size over an 11-week period, at which time skin punch biopsy revealed an infiltrative pattern of well-differentiated blood vessels leading to an interpretation that the lesion was a well-differentiated hemangiosarcoma. The second lesion was revealed when the dog had its fur shaved in that area during surgical preparation to excise the antebrachial lesion. No other skin lesions were found on the dog. Microscopically, there was a widely disseminated and infiltrative-like pattern of benign-appearing small blood vessels, which were throughout the superficial and deep dermis and subcutis. Although the disseminated nature suggested malignancy, the histologic appearance of well-differentiated small blood vessels and nonprogressive clinical features indicate that the lesions were benign. The dog has been followed for 6 years and to date has no evidence of progression of the antebrachial lesion or shoulder lesion. To the authors' knowledge, this is the first report of a congenital angiomatosis-like lesion in a young dog, with extensive involvement of the forelimb.