It will scare the biscuits out of you ... GUARANTEED! With that nagging "C" word drifting about the back of your mind, your first fear is that your dog might have cancer. Setting in motion your search for an answer as to what this lump is you make a quick trip to the I hope that lump isn't serious.
"How long has this been here?" the veterinarian asks. "Just found it yesterday, doctor," you respond.
"Let’s see if we can find any others," says the doctor as experienced and sensitive hands work the dog over. Sure enough, "Here’s another one just like it!" says the doctor as she places your hand right over the small, round, moveable soft mass under the skin of the dog’s flank.
"I think these are what we call Lipomas, just fat deposits under the skin. They are very common and usually present no problems," says the doctor. Your relief at hearing the good news is cut short as the doctor continues …
"However, we honestly do not know what these lumps truly are unless we examine some cells under the microscope. So I’d suggest that we do a simple needle biopsy, place some cells on a slide and send the slides to a veterinary pathologist for a definite diagnosis."
The doctor in this case is being thorough and careful. How true it is that a definitive diagnosis of "what it is" simply cannot be made without microscopic examination of the lump’s cells. A veterinary specialist in pathology is the final authority and judge when it comes to shedding light on these lumps and bumps that we too often find on our canine pals.
The lipoma is one of the most commonly encountered lumps seen by veterinarians during a physical exam. These soft, rounded, non-painful masses, usually present just under the skin but occasionally arising from connective tissues deep between muscles, are generally benign. That is, they stay in one place, do not invade surrounding tissues and do no metastasize to other areas of the body. They grow to a certain size and just sit there in the tissues and behave themselves.
Most lipomas do not have to be removed. Occasionally, though, lipomas will continue to grow into huge fat deposits that are a discomfort to the dog and present a surgical challenge to remove. And even more rarely, some lipomas will be malignant and spread throughout the dog’s body.
Is it a tumor?
And therein lies the true challenge in dealing with lumps and bumps on dogs -- we simply cannot predict with 100% accuracy just what any of these foreigners will do. So we do the best we can by removing them when indicated or keeping a close guard over them so that at the first sign of change they can be removed.
Not every lump or bump on your dog will be a tumor. Some superficial bumps are due simply to plugged oil glands in the skin, called sebaceous cysts. Skin cysts can be composed of dead cells or even sweat or clear fluid; these often rupture on their own, heal, and are never seen again. Others become chronically irritated or infected, and should be removed and then checked by a pathologist just to be sure of what they are. Some breeds, especially the Cocker Spaniel, are prone to developing sebaceous cysts.
And yes, the sebaceous glands in the skin do occasionally develop into tumors called sebaceous adenomas. According to Richard Dubielzig, DVM, of the University of Wisconsin, School of Veterinary Medicine, "Probably the most commonly biopsied lump from dog skin is a sebaceous adenoma. This does not mean it is the most commonly occurring growth, just that it is most commonly biopsied." Fortunately this type of skin growth rarely presents trouble after being surgically removed.
So how are you to know which lumps and bumps are dangerous and which can be left alone? Truthfully, you are really only guessing without getting the pathologist involved. Most veterinarians take a conservative approach to the common lipomas and remove them if they are growing rapidly or are located in a sensitive area.
However, caution needs to be observed because even the common lipoma has an invasive form called an infiltrative lipoma. For example, when a nasty looking, reddened, rapidly growing mass is detected growing on the gum aggressive action is indicated. Also, keep in mind that not all lumps and bumps are cancerous, and some are fairly innocent and do not warrant immediate surgery.
Cysts, warts, infected hair follicles, hematomas (blood blisters) and others do cause concern and can create discomfort for the dog, though non-cancerous lumps have less health impact than cancerous growths.
Cancerous growths can be either malignant or benign, and occasionally even share characteristics of both. Malignant lumps tend to spread rapidly and can metastasize to other areas of the body. Benign growths tend to stay in the place of origin and do not metastasize; however they can grow to huge proportions (see such an example of inoperable tumor pictured on the right).
Mammary gland tumors, mast cell tumors, cutaneous lymphosarcoma, malignant melanoma, fibrosarcoma and many other types of tumors with truly scary names command respect and diligent attention on the part of dog owners and veterinarians.
Below are the most common methods of finding out "what it is" …
Some ulcerated masses lend themselves to easy cell collection and identification by having a glass microscope slide pressed against the raw surface of the mass. The collected cells are dried and sent to a pathologist for staining and diagnosis. Sometimes the attending veterinarian will be able to make a diagnosis via the smear; otherwise, a specialist in veterinary pathology will be the authority regarding tumor type and stage of malignancy.
Many lumps can be analyzed via a needle biopsy rather than by total excision. A needle biopsy is performed by inserting a sterile needle into the lump, pulling back on the plunger, and "vacuuming" in cells from the lump. The collected cells are smeared onto a glass slide for pathological examination. Usually the patient isn’t even aware of the procedure. Total excision of the mass is attempted if the class of tumor identified warrants surgery.
X-ray and ultrasound evaluations are generally reserved for collecting evidence of internal masses. Most lipomas are superficial and reside under the skin or skeletal muscles. There are other lumps that can be palpated by the veterinarian via manual examination that may require spread of cancer internally (ie., metastasis).
Superficial lumps and bumps do not require that CT Scans be done, so this procedure is usually reserved for internal organ analysis. If a superficial malignant tumor is diagnosed, however, a CT Scan can be helpful in determining if metastasis to deeper areas of the body has occurred.