CONDITION
Nerve Sheath Tumour
A nerve sheath tumour is a growth that arises from the cells that wrap around and support peripheral nerves — the nerves outside the brain and spinal cord that carry signals to and from the limbs, face, and body. These tumours can develop anywhere a peripheral nerve runs, and they tend to grow slowly over weeks to months. In dogs, they occur most often in older animals, and certain larger breeds may be more commonly affected. Owners often first notice a lump under the skin, typically on a leg, or they may observe that their dog is favouring a limb, showing discomfort when moving, or experiencing weakness or altered sensation in a specific area. Because the tumour involves a nerve, signs can include lameness that does not improve with rest, muscle wasting in the affected limb, or changes in how the paw is placed or held. In some cases, a tumour affecting a nerve in the chest or abdomen may cause signs that are less easy to localise. This page explores the signals that may suggest a nerve sheath tumour, what is happening at the level of the nerve and surrounding tissue, how these growths are investigated through imaging and sampling, and the range of approaches that exist for managing them. The goal is to help you understand the nature of the condition and the framework within which decisions are made.
Why this matters now
Nerve sheath tumours tend to appear in middle-aged to older dogs, with most cases occurring after seven years of age. Larger breeds may be represented more frequently in clinical reports, though the condition can arise in dogs of any size. There is no clear seasonal or environmental trigger; these growths appear to develop as part of the gradual accumulation of changes in the cells that support and insulate nerve fibres over the course of a dog's life.
These tumours typically grow slowly, over a period of weeks to months, though the rate can vary between individuals. Early on, the signs may be subtle or intermittent—a slight change in gait or a small lump that is easy to overlook. As the tumour enlarges, it can place increasing pressure on the nerve it surrounds, leading to more persistent lameness, progressive muscle wasting, or altered sensation in the area served by that nerve. In some cases, growth remains localised for an extended period; in others, the tumour may eventually involve nearby tissues or, less commonly, spread to distant sites.
Signals & patterns
Early signals
Subtle lameness or altered gait
The dog may begin to favour one limb, placing weight differently or showing a slight reluctance to bear down fully. This can come and go at first, and may not improve with rest in the way a simple strain might.
Small, firm lump under the skin
A discrete swelling may appear along the course of a limb, often feeling fixed to deeper structures rather than moving freely beneath the skin. It may be noticed during grooming or routine handling.
Mild sensitivity on handling
The dog may flinch, pull away, or show discomfort when the affected area is touched or manipulated, even if there is no obvious external injury. This can be the first indication that something beneath the skin is involved.
Slight muscle softening
The muscles in the affected limb may begin to feel less firm or slightly reduced in bulk compared to the opposite side. This reflects early changes in nerve signalling to the muscle, even before obvious weakness is apparent.
Altered paw placement
The dog may begin to place the paw at an unusual angle or drag the toes slightly, a sign that the nerve controlling fine motor control or sensation in the limb is being affected. This can be intermittent at first.
Later signals
Persistent, non-weight-bearing lameness
As the tumour grows, the dog may become increasingly reluctant or unable to use the limb, holding it up or placing minimal weight on it. The lameness is typically progressive and does not respond to rest or simple pain relief.
Marked muscle wasting
The muscles in the affected limb may become visibly smaller and softer, a process called atrophy, which occurs when the nerve can no longer deliver adequate signals to maintain muscle tone and mass.
Loss of sensation or reflexes
The dog may not respond normally to touch or pressure in the affected area, and reflexes that depend on the involved nerve may be diminished or absent. This reflects significant disruption of nerve function.
Enlarging or ulcerating mass
In some cases, the tumour may grow large enough to distort the overlying skin, which can become stretched, inflamed, or break down. This can introduce secondary complications such as infection or discomfort from the mass itself.
Click to read about the biological mechanisms
How this is usually investigated
Options & trade-offs
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