Canine leiomyosarcoma - Cancer of the muscle tissue

Leiomyosarcoma is often shortened to LMS for ease of pronunciation, and is a type of cancer that affects certain types of muscle tissues in dogs, and which is classed as a smooth muscle cancer. Leiomyosarcoma is not the most common form of soft tissue cancer in dogs, but accounts for anything up to 15% of all canine malignant soft tissue cancer diagnosis, and is one that can take many years of slow development to become apparent, hence being most commonly diagnosed in older dogs.

In this article we will look at leiomyosarcoma in dogs in more detail, including what type of dogs are most likely to be affected by the condition, how to identify its onset, and what can be done about it. Read on to learn more about leiomyosarcoma or LMS in dogs.

What is leiomyosarcoma?

Leiomyosarcoma is a type of cancer that affects certain types of muscle tissue, most commonly those of the intestine and stomach. However, it can also potentially affect any area of muscular soft tissue, including, potentially, the area surrounding the spleen.

LMS tends to occur as a localised lesion or tumour that affects one specific area of the body in the first instance, although it is a fairly aggressive type of cancer that will often spread quickly to the surrounding organs and tissue.

What type of dogs are at risk of the condition?

Dogs of any breed or type can develop LMS, and it affects male and female dogs equally frequently. It is rarely diagnosed in dogs under the age of around six or seven, and most commonly presents in dogs over the age of ten, and so can fairly be classed as mainly a condition of old age.

Whilst no specific hereditary predisposition to LMS has been identified in any one breed more than others, leiomyosarcoma tends to be more prevalent in large and giant breeds of dogs than smaller ones, so for those that own very large dogs, such as the Newfoundland or Bernese mountain dog, it is something that you should be aware of.

What are the symptoms of LMS in dogs?

Owners of large and giant breeds of dog, and those that are over the age of around eight should be alert to the potential symptoms of leiomyosarcoma, and because the condition affects the internal organs without any outward physical symptoms, and because it tends to be slow in onset, it can be hard to identify LMS until it becomes quite pronounced.

If you own an older dog, it is of course very important to make sure that they receive an annual health check with your vet, so that your vet can spot the signs of any problems in the making as soon as possible, and you may even want to schedule six-monthly consults if this is deemed appropriate for your own dog.

Some of the main symptoms of LMS to be on the lookout for, and that you should discuss with your vet if you identify them include:

• Generalised lethargy, depression, and lowered activity levels; however, these can in some cases be hard to differentiate from the natural age-related slowdown of the senior dog.
• Weight loss without any specific obvious cause, which is not deemed to be a side effect of aging.
• Diarrhoea, and/or vomiting, or other signs of digestive discomfort.
• Generalised signs of internal pain or discomfort, such as problems settling down, yelping when touched in the stomach region, or appearing preoccupied with the stomach area.
• In pronounced cases of LMS that are affecting soft muscle tissue on the outside of organs close to the skin, you may be able to feel the lumps and bumps caused by tumour formation if you gently palpate your dog’s abdomen and stomach.

What is the treatment and prognosis for affected dogs?

The sooner you can get a definitive diagnosis of LMS in your dog, the better their prognosis for survival and recovery will be, so it is particularly important for the senior dog to get checked out by the vet if you are concerned that something is amiss.

Your vet will need to undertake a physical examination of your dog, taking into account their age and health history, and they will also likely run a blood panel and urine test too, to check for any anomalies. X-rays and ultrasound scans may be required too, and once your vet has identified a potential mass, tumour or something else that should not be there, they will take a biopsy of it to get a formal diagnosis of the problem.

If leiomyosarcoma is diagnosed, how advanced it is and how large an area of the body it is affecting will dictate the best way to proceed, as will your dog’s age and general health.

If the tumour is localised, small and has clear boundaries, generally, surgical removal is the best option for removing the tumour and preventing its spread. If this is not possible, radiotherapy or chemotherapy may be used instead, or your vet may also decide to use these in combination with surgery to remove the main part of the tumour.

The eventual prognosis for affected dogs can vary considerably; splenic tumours can be complex and challenging to treat, and may require the removal of the spleen to treat. If this is not possible, the eventual prognosis is likely to be guarded to poor, whilst for other locations in the body, depending on how advanced they are and how old the dog is at the time of diagnosis, dogs may live for several more years after treatment.