New lumps and bumps pop up all the time in our furry friends, especially as they get older. There are many different kinds of lumps pets can develop; some are benign and require no treatment, whereas others are malignant and necessitate surgical removal. When you bring your pet into your veterinarian to check out a lump, we will usually recommend a fine needle aspirate to help determine what it is. This involves inserting a needle into the lump, poking the needle around inside, blowing out the exfoliated cells and debris onto a microscope slide, and then examining it. This technique can usually give your veterinarian a diagnosis. A fine needle aspirate is not the same as a biopsy. A biopsy involves looking at a large chunk of the lump that has been surgically removed, and will always provide a definitive diagnosis; whereas an aspirate is merely a tiny sample of the cells inside it.

One of the most common skin tumors we see is a lipoma. A lipoma is a benign fatty tumor that resides in the subcutaneous tissues (under the skin). These tumors tend to be soft, squishy, and easily moveable. Lipomas are very common in older Labrador Retrievers, Pointers, and Golden Retrievers, although they can occur in any breed. They also can occur in any location on the body but are most common on the trunk. Some dogs develop multiple lipomas. If desired, they can be removed surgically, as they can sometimes be very large. Lipomas will never spontaneously regress on their own and they may grow in size. Still, a diagnosis of a lipoma is usually a relief to most owners as no treatment is needed.

A very common malignant skin tumor is a mast cell tumor. Mast cell tumors are composed of mast cells, which are immune-regulatory cells filled with tiny histamine and serotonin granules. When a mast cell tumor is touched or messed with, the cells release these granules and the tumor grows and can become ulcerated and red. When left alone, the tumor can shrink back down. Therefore, these tumors fluctuate in size and are often itchy to the patient. Mast cell tumors can be found anywhere, on the skin or under the skin, and can be firm or soft in consistency (hence the importance of obtaining a fine needle aspirate, even if the lump looks and feels like a lipoma). Mast cell tumors must be surgically resected and ideally submitted for a biopsy. A biopsy will determine the tumor’s “aggressiveness” or grade. Grade I mast cell tumors require no treatment beyond surgical resection, whereas grade III mast cell tumors are more aggressive and warrant careful monitoring for recurrence or metastasis.

Most people don’t think young dogs develop skin tumors, but there is one kind of tumor that occurs almost exclusively in dogs <5 years old. A cutaneous histiocytoma is a benign tumor made up of cells called Langerhans cells. These tumors sit on the surface of the skin and are typically button-shaped and bright red. They can be surgically resected, especially if the pet is licking excessively and causing it to bleed. However, one interesting characteristic of these tumors is that they can spontaneously fall off on their own. This can take several months though, so if your pet is bothered by its histiocytoma, surgical resection is the answer.

Papillomas or warts are common in dogs both young and old. In young dogs (usually <1 year of age), papillomas tend to occur on the lips but can be found on other mucous membranes as well. They are rough and cauliflower-like on close examination. Some dogs develop several papillomas; in fact, finding only one is rare. Papillomas in young dogs are caused by a papillomavirus. Thankfully, by the time the dog and his/her immune system has matured, they almost always fall off on their own and are never a problem. Older dogs often develop “papilloma-like” tumors, although these are technically sebaceous cysts. These are small, benign tumors and are particularly common in Cocker Spaniels. They do not fall off on their own but can be surgically removed if they become unsightly and/or bleed easily.

This is a brief list of some of the more common lumps we see in our day-to-day practice. Obviously, there are others not covered here. If you find a new lump on your pet, call us! We will be more than happy to help determine what it is, as well as the appropriate course of action.


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