Generalized nodular dermatofibrosis in six Alsatians.

Abstract

The condition we have named “generalized nodular dermatofibrosis” has not been described in domestic animals. We present six cases which occurred in dogs examined in the past two years. Six Alsatians between seven and nine years of age had multiple, firm, well-circumscribed nodules in the skin and subcutis all over the body with the most common localization on the legs (fig. 1). The nodules varied from a few millimeters to 4 cm in diameter. They sometimes were coalescent and usually were covered by intact epidermis. In a few locations there was ulceration and secondary inflammation. The nodules had grown slowly over a period of 1% to four years and did not seem to hinder the animals. All dogs were in good physical condition. Microscopic examination of biopsies revealed dense, well-differentiated, strongly van Gieson-positive collagen fibers and a few fibrocytes. Ultrastructurally the collagen fibrils had a constant diameter of about 90 nm and a regular cross banding (fig. 2). The tumors were localized in the dermis and extended into the subcutis (fig. 3). They were well-circumscribed but had no capsule. Three and 18 months after the first presentation, two dogs returned in poor health. Radiographic examination revealed enlarged kidneys, thus, both dogs were euthanatized and necropsied. All kidneys had multiple cysts containing dark-red soft tissue. Histologically the lesions were poorly differentiated renal cystadenocarcinomas (fig. 4). In one dog metastases were found in the spleen and the right ilium. One other dog was euthanatized but not submitted for necropsy. The remaining three dogs are still alive and in good health. In man, there are four comparable conditions: generalized congenital fibromatosis [I], shagreen patches [3], dermatofibrosis lenticularis of the Buschke-Ollendorff Syndrome [5], and disseminated connective tissue nevi [2]. The lesions of our dogs differed from these conditions in several respects. There were no bone lesions as found in generalized congenital fibromatosis and dermatofibrosis lenticularis of the Buschke-Ollendorff Syndrome, and no changes in the ultrastructure of the collagen fibrils as found in shagreen patches and disseminated connective tissue nevi. Shagreen patches and dermatofibrosis lenticularis are inherited in an autosomal dominant way. We found common ancestors in the pedigree of three dogs, but the material is too limited to be conclusive. Hence, the etiology of the nodular proliferation of collagen tissue in the Alsatians remains unknown. We assume it was benign neoplastic change since there is no evidence of reactive fibrosis. In the two dogs with renal carcinoma, no epithelial tumor cells could be found in the dermal nodules. The coincidence of dermatofibrosis and renal carcinoma probably is accidental since the nodules persisted for more than four years, whereas the carcinoma must