Congenital and Hereditary Neoplasms and Hamartomas in Animals

Congenital neoplasms are common in large animals. Mastocytosis, melanocytosis, cutaneous lymphosarcoma, and vascular hamartomas are found in calves. Melanocytomas, which are thought to be benign, may also arise shortly after birth in calves and may be hereditary.

Melanomas are observed in Duroc-Jersey and Sinclair miniature pigs as familial traits. These may undergo spontaneous remission or may behave as malignant tumors. Piglets have also been described with vascular hamartomas and with congenital fibropapillomatosis, which is likely infectious.

Congenital tumors are rare in dogs and cats. One dog with a giant congenital pigmented nevus had a malignant melanoma develop within the lesion. In cats, familial benign mastocytosis is described in young Siamese cats.

Nodular dermatofibrosis is a syndrome of multiple collagenous nevi that occurs in some families of German Shepherd Dogs. Affected dogs are adults. Dozens of skin lesions may occur, and those on the feet often ulcerate, deform the feet, or cause lameness. This syndrome is a cutaneous marker for renal cystadenocarcinoma and uterine leiomyoma. The gene variant in this syndrome has been identified as flcn. Abdominal ultrasonography is recommended in dogs with suspect lesions to screen for renal and uterine disease.

Progressive dermal collagenosis is similar to nodular dermatofibrosis and affects postpubertal male miniature pigs. It is thought to be hereditary and is characterized by symmetrical, firm plaques on the trunk that consist of thick collagen bundles replacing the normal dermis and panniculus. A connection with internal malignancy has not been reported. A genetic test is available for this disorder.

Feline maculopapular cutaneous mastocytosis (urticaria pigmentosa) is caused by mast cell hyperplasia. Affected cats have multifocal, partially coalescing macular and crusted papular eruption on the head, neck, and legs. Diagnosis is made by skin biopsy. There is evidence of a familial history and has been commonly reported in Sphynx cats and noted in the domestic shorthair. Affected cats may respond well to treatment with combined oral dexamethasone and cetirizine hydrochloride.