Topical imiquimod in the treatment of two cutaneous melanocytomas in a dog

Imiquimod is a topical biological response modifier that has been shown to be useful in the treatment of several viral and nonviral skin tumours in humans and animals. Lentigo maligna (melanoma in situ) is common in older humans, and can be successfully treated with imiquimod. Melanocytomas are common skin tumours in dogs, and although surgical removal is the treatment of choice, tumour location and patient morbidity can make excision difficult in some cases. This case report describes the use of imiquimod to successfully treat two melanocytomas in one dog, including clinical results, histopathology and immunohistochemical staining, as well as a comparison with lentigo maligna treatment in humans. To the best of the authors' knowledge, this is the first report of the use of imiquimod to treat canine melanocytomas, and the first description of post-treatment histopathology and immunohistochemistry after imiquimod use in companion animals.