Canine and Feline Skin Tumors

Introduction

Due to its complex structure a large variety of tumors may arise in the skin (Table 1), as can secondary (metastatic) tumors. Approximately 2/3 of all canine cutaneous tumors are solitary, benign lesions originating from the epithelium or from adnexal structures, whilst in the cat malignant tumors are more common than benign ones. The etiology of most skin tumors is still unknown, but roles of UVB light exposure, hormonal and viral etiologies are demonstrated in some tumors. This article provides an overview of the more common skin tumors affecting dogs and cats but excludes soft tissue sarcomas. A presumptive diagnosis of a solitary skin tumor may be made on clinical examination, but multifocal lesions may be harder to distinguish from other dermatological conditions. Fine needle aspiration (FNA) is a quick, minimally invasive and useful technique for assessing any mass within the skin. In some cases (e.g. mast cell tumors, cutaneous lymphoma) cytology may provide a diagnosis, although histological examination of the tumor is still required to grade the lesion. Fine needle aspiration of local lymph nodes is also useful to assess metastatic spread. Skin punch, needle or incisional biopsies are required for a definitive histological diagnosis. Collection of a representative sample of tissue is important and is discussed elsewhere in this issue. Excisional biopsy (local resection of the whole mass) should only be performed after careful consideration; it can have disastrous consequences if used inappropriately and the opportunity for curative treatment may be lost forever. Excisional biopsy is appropriate in cases where prior knowledge of tumor histology/ grade would not alter the surgical approach. [...]

Key Points

• The skin is the most common site for neoplasia in dogs and cats.
• A huge number of different tumors may arise in the skin, and the prognosis can vary from excellent to hopeless depending on the tumor type.
• Accurate identification of the tumor is essential to allow for informed treatment options to be considered.