It's every rat owner's worst nightmare: discovering a tumor on a pet rat. Rats are very prone to developing tumors and masses, some of which are benign and a few of which are cancerous. The first step to determining the best course of treatment for a rat with a tumor involves determining what type of tumor is present on the rat's body.
Diagnosing a Rat's Tumor With X-Rays
There are several routine steps that can be taken to diagnose a rat's tumor. Following an examination, the next step toward diagnosis of a rat's tumor involves taking x-rays.
The x-rays, also known as radiographs, will help the veterinarian to determine precisely what tissues or structures have been affected by the rat's mass. The veterinarian will examine the borders of the mass. Benign, non-cancerous tumors usually have a clear line of demarcation. Benign tumors are usually encapsulated with a membrane, which separates the mass from the surrounding tissue and structures. Malignant tumors in rats don't usually have a clear line of demarcation; they are often intermingled with surrounding structures and tissue.
When examining a rat's x-rays, the vet will also look for signs of metastasis - the spread of malignant tumor cells to remote regions of the rat's body.
Notably, sedation is usually required to obtain a good quality x-ray for a pet rat. The same can be said for many other pets as well - some degree of sedation is often required in order to prevent the movement that's necessary to get a high-quality x-ray film.
Rat Tumor Diagnosis Through Fine Needle Aspirates and Cytology
The next step in identifying the type of tumor in the rat's body involves performing a fine needle aspirate. A needle is injected into the tumor and the veterinarian obtains a small sample of the tumor's cells, which are then examined under a microscope. In many cases, the cytology sample will be sent out to a specialist at a lab who will attempt to determine the precise type of cells present in the rat's tumor.
In about 50 percent of cases, a determination can be made as to whether the rat's mass is benign or malignant. Fine needle aspirate procedures are not always conclusive, particularly in cases where the cell concentration is sparse - this makes it difficult to obtain a good cell sample.
"In some cases, it's like throwing darts at a dartboard, only you have no idea where the bull's eye is located. With luck, you may hit the bull's eye and get a good cell sample that will lend itself to diagnosis. Or you may miss the bull's eye altogether and end up without a good cell sample from the rat's tumor. This is the case with all fine needle aspirate procedures - not just those that are performed in pet rats," explained Dr. Michael Levine, DVM.
Lumps and Bumps in Hairless Rats
It's important to note that hairless rats are very prone to developing lumps and bumps. These lumps tend to be superficial and benign. Most often, the bumps are sebaceous cysts, caused by sebum, oil, bacteria and dirt that accumulates on the hairless rat's skin.
The rat's cysts can be drained and surgically excised. Infected cysts will require a course of antibiotics. Surgical removal of the cyst is the only effective measure, as once a pore is damaged, cyst formation is apt to continue at the site.
Benign Tumors and Malignant (Cancerous) Tumors in Rats
The majority of tumors that develop in rats are benign and non-cancerous. Mammary tumors are very common in female rats in particular. Female rats are at a significantly higher risk of developing tumors.
Most benign tumors in rats and other animals will be encapsulated with a membrane, which forms the appearance of clearly delineated edges, while a cancerous mass will usually have less clear boundaries and edges. Tumors may be relatively soft, or hard like a rock - it varies on the type of mass and other factors, such as calcification. Calcification is a hardening of the mass due to the formation of calcium deposits and it can occur on benign tumors, malignant tumors and even in areas of infected tissue.
The recommended treatment for a benign tumor will vary depending on factors like the tumor's rate of growth, the tumor's location on the rat, the rat's age and general health. Surgical removal of the tumor is among the most common treatments for a rat. Unfortunately, measures like chemotherapy and radiation are not currently performed on rats who are suffering from cancer.
A benign tumor in a rat is less harmful than a cancerous, malignant mass because it will not metastasize, meaning it will not spread to other regions of the body. Cancerous tumors can be surgically removed, but the cancer has often spread to other parts of the body as a result of metastasis, leading to a poor prognosis. On the other hand, surgical removal of a benign non-cancerous tumor can be successful and with any luck, the rat will recover and continue on to live a happy, healthy life.
Mia Carter - Mia Carter - Journalist, Producer/Editor & Web Writer. Carter's work has appeared on CBS and CNN.com.
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