Much like the human epidermis, a cat's skin can demonstrate all manner of moles, bumps, tags and cysts that are completely harmless. And of course sometimes, as with human skin, these lesions can be indicative of a deeper health concern. It's important to know the good from the bad and to regularly monitor your kitty's hide for any unusual changes.
Features of Moles
Moles are very common and normal elements of cats' skin. Most moles are benign skin markings that can cover the entire spectrum of flesh tone colouration, from dark to light. They can be so small as to be nearly invisible, or quite large, and they can be hidden under the cat's fur or visible around the face, anus, or other exposed areas. They will generally maintain their colour, shape and size over the life of the animal. Some cats will also demonstrate small, dark, mole-like spots on their eyelids, lips or ears. These spots are called "lentigo" and are also quite harmless.
Features of Skin Tags
Feline skin tags are rarer than moles, but no more dangerous. They are fleshy, discoloured epidermal flaps that can grow as large as a grape, though they are usually quite small. They do not create pain or discomfort, and contain no fluid. They are generally found near the folds of the cat's skin, such as around the neck or between where the legs meet the abdomen. It can be tempting to try and pick or cut off a skin tag, but remember that they are an extension of the cat's skin and will hurt and bleed if damaged.
As in humans, feline moles that change in colour or size can be indicative of a deeper health concern. Such moles are called "melanomas." Though they are often benign, they can also be a sign of skin cancer, the second-most common type of cancer in felines. Melanomas are generally very dark in colouration, either brown or black, and can manifest anywhere---under the fur or on and around the cat's face, anus and other areas unprotected from the sun. Any mole that appears to be a melanoma should be checked out by a veterinarian immediately.
Fur covers most cats' bodies, which can make it difficult to visually detect unusual moles and other skin irregularities that might be cause for alarm. Fortunately, the kinds of epidermal features indicative of skin cancer and other ailments are usually raised, swollen, or even painful to the animal, meaning they can be detected by touch. It is important to acquaint your cat with regular human touch, and regularly check her skin through gentle massage and brushing. During this process, you can also part the cat's fur and look for melanomas.
If your cat's skin tags or moles are benign there is no need to have them removed, though some owners have them removed for cosmetic reasons. Veterinarians can cauterise skin tags to remove them or freeze them off using liquid nitrogen. Moles can also be burnt or frozen off, but due to their deeper position in the skin, they must occasionally be surgically removed. The surgery is not invasive, but must sometimes be done in stages depending on the size and thickness of the mole.