Skin Masses

Skin masses are more annoying than anything else. However, some of them can be deadly. This article will discuss some of the types of skin masses that commonly occur in small animals, the warning signs of problem masses, and diagnosis/treatment options.

Types. Skin and subcutaneous (under the skin) masses can generally be divided into two broad categories: benign and malignant. The ability to spread or reoccur (malignancy) is one of the most important things to consider when deciding if a skin mass should be removed or if it can be left and monitored. The common benign, or relatively harmless, skin masses include cysts, abscesses, warty-like growths, lipomas, histiocytomas, and mammary adenomas, among others. The common malignant, or cancerous masses that have the tendency to spread or reoccur, include mast cell tumors, lymphosarcoma, mammary adenocarcinoma, and fibrosarcoma, among others.

Warning Signs. Ideally, a veterinarian should examine all skin and subcutaneous masses. Many malignant masses can be cured if they are taken care of early in the course of the disease. Delaying treatment can have negative consequences for some types of tumors. Masses that should raise suspicion, and therefore warrant more aggressive diagnosis and treatment, include: 

1. Masses that weep or ooze any fluid, blood, or debris.

2. Masses that pop up suddenly or grow quickly.

3. Masses that pop up in multiple places within a short time frame.

4. Masses that are very firm or hard.

5. Masses that are painful when touched.

6. Masses that the pet licks or chews at. 

7. Masses in the mammary area.

Diagnosis. Several diagnostic options are available to determine if the suspect skin or subcutaneous mass is something to worry about. In some instances (cysts, abscesses, lipomas) direct examination of the mass on the cut section can reveal the nature of the mass that is present. However, in most instances, the naked eye cannot distinguish the type of mass that is present and a closer examination of the cells that make up the mass is warranted. 

There are three ways to gather samples to determine if a mass is benign or malignant. The first is a fine needle aspirate (FNA). With this technique, the veterinarian will use a small gauge needle to take a small sample of cells from the mass. The cells can then be ejected onto a slide, stained, and examined for characteristics of malignancy. Secondly, a true cut biopsy can be taken. With this technique, a small biopsy instrument is used to take a tiny slice of the tumor. The slice is then submitted to a lab for histopathology (biopsy). Third, the entire mass can be surgically removed, in total, and submitted to a lab for histopathology. 

There are distinct advantages and disadvantages to each of these methods. Obviously, a fine needle aspirate is the easiest, cheapest, and least invasive method to diagnose a benign or malignant tumor. It can be done quickly without any anesthesia since only a small needle is used. However, in certain instances, it may not be the most accurate method. Since only a few cells are taken from the mass, it is possible to misdiagnose a mass based on a fine needle aspirate alone. A true cut biopsy can also have the same problem, especially if it is a very large mass. However, since a larger portion of the mass is taken diagnostic accuracy increases, true cut biopsies can be done with local or general anesthesia, depending on the size and location of the mass. The most accurate method of diagnosis, surgical removal, is the most expensive option and will often require sedation or anesthesia. However, surgical excision has the added benefit of removing the entire mass whereas the other means of diagnosis do not. If the mass is malignant an additional surgery to remove the mass is not necessary, unlike if a fine needle aspirate or true cut biopsy is performed. 

Treatment. Once the mass has been identified as being a benign or malignant type of tumor, the best method of treatment can be determined. In the cases of benign tumors, one option is to leave the mass alone and not pursue complete surgical excision. This choice may be appropriate for masses such as warts and lipomas provided they are not bothering the pet. The other option is to have the mass destroyed or removed. In cases of malignant tumors, surgical removal of as much of the mass as possible is recommended. Additional treatments including chemotherapy and radiation may be necessary if the tumor has a high likelihood to spread to distant sites in the body or if the mass has already spread. The recommendations for additional protocols will vary greatly depending on the type of tumor that has been identified.

Current acceptable methods of mass removal, for benign and malignant tumors, include excision with a scalpel, excision with a laser, and excision with electrocautery. Current acceptable methods of mass destruction include freezing (cryotherapy), burning (electrocautery), and radiation. All excision methods involve cutting the mass out of the surrounding tissue. The only difference is the type of instrument used to do the cutting. Cryotherapy involves using a liquid nitrogen delivery system to freeze affected tissue. With successive freezing, the mass will decrease in size and fall off. It is best suited for small, superficial masses. Electrocautery involves using electricity to burn a mass. It is also best suited for smaller, superficial masses. Radiation can be used as a means of mass destruction or treatment for malignant masses.

The information provided is for educational purposes only and is not intended to take the place of your regular veterinarian. Please do not hesitate to contact your regular veterinarian if you have questions regarding your pet.