Nodules are lumps found on a dog's skin. Any nodule found on a dog's skin should be examined by a veterinarian to determine exactly what it is, but knowing the different types and what they look like can help you get a better idea of what the lump might be. Lumps found on the skin do not automatically mean a dog has cancer and it's important to know all the facts before assuming the worst. Recognising and treating potential health problems early is the key to keeping your dog healthy.
Cancerous tumours on a dog's skin can include sebaceous adenoma, epidermoid carcinoma and breast tumours. Nodules caused by sebaceous adenoma form in the oil-producing glands in the skin and are usually light-coloured, less than 1 inch long and tend to resemble cauliflower. Epidermoid carcinoma are hard, flat grey-coloured ulcers that usually occur on the legs and feet. Breast tumours are often hard lumps found around the mammary glands around the dogs nipples. Not all breast tumours are cancerous though so tests are often needed to find out what type of tumour it is.
Basal cell tumours and lipoma are two types of benign tumours found in dogs. Basal cell tumours are slow growing tumours often found on the neck and head. They are usually filled with fluid and can sometimes open up and leak. Basal cell tumours do have the potential to develop into cancerous tumours in some cases. Lipoma are very common benign fatty tumours that usually appear as soft, domed nodules and can grow very large. Lipoma tumours are often found on the head, neck, shoulders and back. These type of tumours are considered harmless and they aren't usually removed or treated.
Sterile nodular panniculitis is common skin disease where the fat under the skin becomes inflamed. The inflammation develops into nodules underneath the surface of the skin. The enzymes released from the inflammation turn the fat into liquid and will cause the nodules to swell. The nodules sometimes rupture and leak an yellowish oily fluid. Cuterebra is another disease that can cause nodules. Cuterebra usually appear on the head and neck. The nodules are caused by the larvae of the cuterebra fly burrowing under the skin. A small hole forms on the nodule that the larvae uses to breathe through and eventually escape from.
Cystic warts are often firm bumps on the skin that are caused by a viral infection known as papillomavirus. Warts are often round lumps and tend to be skin-coloured or whitish-yellow. The warts can spread and sometimes appear in clusters on the dog's body. Other nodules and lumps on the skin can also be caused by fungal infections which produce non-pigmented growths on the skin. Fungal infections are often caused by bacterial organisms in mould, plants or soil. Infected abcesses can also cause firm or fluid-filled nodules and are usually the result of bite wounds from other animals.