Tumors in dogs can develop in many parts of the body, including the skin, lymphatic system, mammary glands, bones, and internal organs. Common types of tumors and cancers in dogs include lymphoma, mast cell tumors, mammary tumors, osteosarcoma, and hemangiosarcoma. Some dog tumors are relatively easy to notice because they appear on or beneath the skin. Others develop internally and may not cause obvious signs during the early stages.
