Lumps come in all shapes and sizes. The size, location, shape and feel of a lump may help your veterinarian take an educated guess at what it is. But just remember veterinarians don’t have x-ray microscopic vision, which means we can’t give an accurate diagnosis without some extra tests.
Small skin bumps (papules) and larger skin lumps (nodules) are very common in dogs. Many of these are benign growths of the skin, such as warts or follicular cysts. Follicular cysts occur when the pores of the skin become blocked causing a build up sebaceous fluid. These nodules occur within the layers of the skin, (so can be moved by moving the skin) and are quite firm to touch. But some skin masses are not benign. Just like us dogs and cats can develop melanoma, which often present as a dark coloured nodule in the skin. A common skin cancer of boxers and bull terriers (can affect other breeds) is a cutaneous haemoangiosarcoma. These tumours present as small, red and raised blisters on the skin, particularly the skin of the abdomen and chest.
Lipomas are one of the most common, and there for over diagnosed, skin nodules of dogs and cats. A lipoma is a benign tumour of the fat tissue. They generally sit just under the skin, in the subcutaneous fat, but can also be found in between muscle layers. Many vets diagnose lipomas by ‘feel’ and although they are right most of the time this is not an accurate way to tell the difference between a benign and cancerous growth.
Mammary tumours are common in entire (not spayed) female dogs. The risk of developing a mammary tumour increases from 0.05% in dogs spayed before their first heat to 26% in dogs that have had more than one heat. So mammary cancer prevention is a really good reason to get your female dog spayed! Mammary tumours can be aggressive so should be taken very seriously and checked by your veterinarian.
There are countless other lump and bumps you could find in your pet, both benign and cancerous, but the point I would like to make here is that there is no way to know for sure. A very simple test available to veterinarians is to perform a Fine Needle Aspirate (FNA). A FNA involves taking a small needle and inserting into the lump. The material aspirated from the lump is then placed on a microscope slide, stained and viewed by the vet. Often your veterinarian can give you a quick idea of whether this lump looks benign or if it needs more testing. This test is affordable and minimally invasive; almost all dogs and cats will tolerate this as they would any other needle.
If the FNA is not diagnostic, or the cells look suspicious, your veterinarian will often recommend a biopsy. In a large mass this biopsy may just be a section but with smaller masses it is often easier to remove the whole thing and send it away to be identified. Although mass removal surgery is costly it is cheaper the smaller and less invasive the mass is – so don’t just sit and wait.
So when should you take your pet in for a lump check? Any lump that has been there for over two weeks or is growing rapidly or has become larger than the size of a pea should be investigated. Lumps that have been there for years should be aspirated once a year, at your pet’s annual checkup, to ensure they haven’t changed or grown. If you have one of those ‘lumpy’ pets (I am picturing a beautiful Labrador) try keeping a little drawing of all the lumps and their sizes to help you remember the size, shape and location of their masses.
And just remember if your veterinarian tells you a lump is ‘just a lipoma’ based on feel you should request a fine needle aspirate.