Skin tumors are the most common tumors in dogs and cats. More than half of skin tumors are benign (especially in dogs), but all skin lumps deserve attention for the possibility of malignancy. Taking a few cells out of these tumors (fine-needle aspiration cytology) can help determine benign from malignant tumors. Management may include observation (only if it is conclusively benign), surgery, cryosurgery or, rarely, radiation or chemotherapy. Outcome ranges dramatically based on tumor type, site, size, species and degree of malignancy.