Dogs can develop several types of skin cancer, including mast cell tumors, melanomas, and squamous cell carcinomas. None of these conditions is especially common in pugs, although mast cell tumors are often seen in short-nosed breeds as a whole. With your pug's smooth coat, signs of skin cancer can sometimes be obvious in the early stages, so pay attention to anything unusual.
Mast Cell Tumors
Mast cell tumors make up 10 to 20 percent of the skin tumors seen in dogs. Mast cell tumors have many nodules and usually look red, hairless, and ulcerated. They can be benign or malignant (harmful) and should be removed surgically. Dogs with malignant mast cell tumors may also need radiation or chemotherapy.
Melanomas develop from cells in the skin that produce melanin, which is what gives your pug the dark pigment on his nose and skin. Melanomas look like brown or black nodules and can occur on the eyelids, lips, in the mouth, on the nail beds, and elsewhere on the body. Skin melanomas are usually harmless, but melanomas in the mouth and nail bed are usually malignant. They can and should be removed surgically, but they often recur. Dogs with melanomas in the mouth don't have a good prognosis.
Squamous Cell Carcinoma
Squamous cell carcinomas are caused by exposure to the ultraviolet radiation in sunlight. They're usually found on lightly pigmented areas of the body. Appearance ranges from a firm red patch to a cauliflower-like growth to a hard, flat, grayish-looking ulcer that doesn't heal. They can be removed surgically or treated with radiation therapy if surgery isn't possible.