Nodular dermatofibrosis is a noncancerous skin disease associated with internal malignancy. It is quite rare and is thought to occur as an inherited cancer syndrome. This condition is most commonly seen in the German Shepherd Dog, but has been also reported in other breeds. This condition evolves as a series of nodules (lumps) which can number in the hundreds and are most often seen involving the areas between the toes and on the legs, but can also develop on the ears and back. The nodules range from a few mm to 3.5 cm and may cause alopecia. The overlaying skin may show some thickening and darkening. In areas of friction the nodules are often ulcerated. Although the lumps do not cause many problems themselves, they are typically associated with the development of cancers of the kidneys and uterus. In this case, the condition is referred to as Canine Hereditary Multifocal Renal Cystadenocarcinoma and Nodular Dermatofibrosis (RCND).
Any German Shepherd having lumps on their legs should be evaluated for the possibility of nodular dermatofibrosis. No dogs with this condition should be used for breeding and all should be screened for the present or future development of kidney or uterine tumors. Affected dogs should be evaluated at least once in three months, since with early recognition the kidney tumors may be surgically removed before the cancer has had time to spread. Pedigree analysis strongly indicates that the syndrome is hereditary, probably in an autosomal dominant pattern. The Birt-Hogg-Dube human syndrome, which is characterized by a variety of organ defects and tumors, shares the development of kidney tumors with nodular dermatofibrosis. Recently, gene mapping localized the suspected gene of canine nodular dermatofibrosis to a small region of canine chromosome 5 that overlaps the Birt-Hogg-Dube location, suggesting that the same gene may be responsible for both conditions.
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Early signs may include lameness caused by nodular growths on the limbs. In many cases, however, these growths may not bother the dog. It has been noted that female German Shepherds are more often affected than male dogs. The skin lesions may precede or occur simultaneously with the kidney tumors. Inflammation is usually minimal. Unlike other skin growths, these lesions are not limited to the dermis (superficial layer of the skin) and their multiplicity is unique. The bulk of the lesions is in the deep dermis. When these lesions are found in female German Shepherds, they should be tested for kidney problems. Computed tomography (CT) examination is useful for the early detection of renal cystadenocarcinomas and for screening suspected carrier dogs before breeding. CT makes it easy to differentiate between cysts and solid tumors in the kidneys.
- Dr. Ackerman's Book of the German Shepherd, Lowell Ackerman.
- Thelma Lee Gross. Skin Diseases of the Dog and Cat: Clinical and Histopathologic Diagnosis