Dogs commonly develop various lumps and bumps on their bodies, including on their legs. Yes, dogs can absolutely get cysts on their legs, along with other types of masses that may be mistaken for cysts. While many of these growths are benign, it is impossible to determine the nature of any lump just by looking at or feeling it. Any new or changing mass found on a dog’s leg requires a prompt examination by a veterinarian. This professional assessment is the only way to establish a definitive diagnosis.
Identifying Common Leg Lumps
The term “cyst” is often used broadly by pet owners, but true cysts are distinct from other common skin masses. A true cyst, such as a sebaceous cyst, results from a blocked oil gland or hair follicle. This blockage leads to a buildup of thick, paste-like material called sebum beneath the skin’s surface. These growths appear as raised bumps that can sometimes rupture, releasing a white, cheesy, or oily discharge. Sebaceous cysts are common on a dog’s legs and are generally harmless, though they can become irritated or infected.
One of the most frequent lumps seen on the lower leg and paws is the interdigital cyst, which is technically a furuncle rather than a true cyst. These are painful, inflamed nodules that form between the toes when a hair follicle ruptures, causing an intense inflammatory reaction. They appear red, swollen, and can rupture to leak blood-tinged or pus-filled fluid. Owners may also find lipomas, which are benign fatty tumors common on the legs and trunk, especially in older or overweight dogs.
It is important to rule out malignant masses like mast cell tumors (MCTs), the most common form of skin cancer in dogs. MCTs can occur anywhere, including the legs, and are known as “the great pretenders” because they mimic almost any other type of lump. They may appear as a small, firm nodule or as a larger, ulcerated, or swollen area. Unlike most other lumps, MCTs can change size rapidly, sometimes getting larger and smaller over the course of a single day if irritated.
Causes Related to Location
The leg area is uniquely susceptible to various lumps due to its anatomy and constant physical contact with the environment. Continuous friction and pressure from walking can lead to mechanical trauma that irritates hair follicles, which causes the formation of interdigital furuncles on the paws. The leg joints, particularly the elbows and hocks, are pressure points where repeated impact can cause thick, fluid-filled sacs called hygromas to form. While not true cysts, hygromas can become infected and present as a large swelling.
The skin on the legs is also prone to foreign body reactions, especially in the paws and lower limbs. Walking through grass or brush can cause materials like splinters or plant awns to penetrate the skin. The immune system attempts to wall off these foreign objects, resulting in an inflamed nodule that can appear similar to a cyst or abscess. Additionally, the high density of hair follicles and sebaceous glands on the legs increases the chance for these structures to become blocked, leading directly to the formation of sebaceous or follicular cysts.
Veterinary Assessment and Treatment
A veterinarian must perform a physical examination to properly assess any mass, noting its location, size, texture, and mobility. Simply observing the lump is insufficient for a definitive diagnosis because benign and malignant growths can have identical appearances. The most common initial diagnostic tool is a Fine Needle Aspiration (FNA). This minimally invasive procedure uses a small needle to collect a sample of cells from the lump. The sample is then examined under a microscope, a process called cytology, to identify the cell type, such as fat cells in a lipoma or mast cells in an MCT.
If the FNA results are inconclusive, or if the mass is highly suspicious, a surgical biopsy may be necessary to obtain a larger tissue sample for detailed analysis. Treatment depends entirely on the diagnosis. For many benign lesions, such as small, non-infected sebaceous cysts or lipomas that do not interfere with mobility, the veterinarian may recommend simple monitoring. Infected masses like abscesses or interdigital furuncles require treatment with antibiotics or drainage. For malignant tumors or benign masses that impede movement, surgical removal is the standard course of action.