Canine Benign Bone Tumors

Overview: Types of Benign Tumors in Dogs

Canine benign bone tumors are classified into 5 different types of tumors:

• Osteoma
• Chondroma
• Multilobular Osteoma and Chondroma (Canine Skull Tumors)
• Osteochondroma
• Enchondromas

Canine Osteoma

Among canine benign bone tumors, an Osteoma is a rare type of tumor. They are found on bone in the skull and around the face. These tumors are very dense, but are comprised of normal bone. They are often confused with exostoses, another type of bone looking growth which is a layer of cartilage which forms underneath a bone.

These types of tumors grow slowly and only result in any symptoms when then begin to negatively impact any adjacent areas.

Canine Chondroma

Chondroma canine benign bone tumors are found in the bone cartilage (tissue that connects bones and aides smooth movement). These tumors are rarely primary (start in the bone), grow slowly and are more often found on flat vs. longer bones.

The tumor is firm and covered by tissue. These tumors are often confused with malignant (neoplastic or cancerous) tumors called chondrosarcomas. These tumors are often misdiagnosed are really enchondromas.

Multilobular Osteoma and Chondroma of the Canine Skull (Canine Skull Tumor)

It is not clear as to whether these types of canine benign bone tumors originate in the skull (primary tumor) or are secondary in nature (triggered by other bones in the skull). They are usually seen in dogs that are on average 7 years old, but a dog is most often between 15 months and 12 years old. Incidence does not vary by sex of the dog or dog breed.

The dog skull tumor grows slowly, and feels like a hard mass, which may invade softer adjacent tissue. 

Symptoms of Canine Skull Tumor

Although the tumor does grow slowly, eventually it can impact adjacent areas and cause clinical symptoms. The most noticeable symptom is a mass sticking out from the skull which looks like a deformity on a dogs head. The dog tumor size varies from .39 inches (1 cm) to 3.9 inches (10 cm). Symptoms vary by tumor location and the areas that it starts to impact:

• Dog Sinus: If the tumor is in the dogs front sinus, then it causes pus in the nose (purulent rhinitis).
• Dog Brain: If the tumor begins to grow into the brain, then problems with the dog's nervous system will start to appear.
• Eye: If the tumor impacts the area behind the eye, the eye will look like it is sticking out or protruded (exophthalmia).
• Jaw: Difficulty opening due to tumors in the temporal bone or zygomatic bone.

Treatment of Canine Skull Tumor

Since these tumors will eventually cause a problem, they are surgically removed. They can recur is the tumor wasn't completely removed. There have been cases where the benign tumors became malignant and then spread cancerous cells to the dog lungs (Pool RR: Tumors of bone and cartilage).

Canine Osteochandroma (multiple cartilaginous)

This type of tumor is found in the bone cartilage and is seen in young dogs in bone that hasn’t yet calcified. Bones commonly affected by canine benign bone tumors are the femur (longest bone in body, extends from pelvis to dog knee) and tibia (dog bone below the knee). After canine skull tumors, it is the second most common type of dog bone tumor. There is a higher incidence in certain breeds such as Great Danes, Saint Bernards and Hounds.

Symptoms of Canine Osteochandroma

Since these tumors usually impact the leg, symptoms are related to walking such as limb weakness, pain and lameness. As indicated in the photo below, you can often seen the tumor protruding off of the bone.

Diagnosis of Osteochandroma

Your Veterinarian will take X-Rays to determine if there is a Osteochandroma tumor. If a diagnosis cannot be made from X-Rays alone, a biopsy will be taken (sample).

In some cases, you can see an enlarged area on the leg as indicated on the wider part of the bone.

Treatment of Osteochandroma

Surgery is used to remove the tumors if they endanger the dog or if removal is desired for cosmetic reasons.

Once the osteochandroma is removed, your dog should make a full recovery. Sometimes the tumor will reappear and can transform into a cancerous tumor (called chondrosarcoma and osteosarcoma).

Canine Enchondromas

Canine Enchondroma is a rare tumor found in the long cavity of the bone. These tumors can exist as single tumors or in groups (enchondromatosis).

This type of tumor has a higher incidence in larger breeds. Multiple X-Rays over a period of time are used to determine is the tumor has changed which aides in getting a definitive diagnosis. They are also found when they cause a fracture at the location of the tumor, where the dog bone tumor caused the bone to thin out.

The tumor is treated with surgical removal. Once removed a dogs prognosis is good.

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References

James M. Giffin MD and Liisa D. Carlson DVM; Dog Owner’s Home Veterinary Handbook
Canine Osteosarcoma, Is There a Cure?

J. Kirpensteijn, DVM, PhD, Diplomate ECVS & ACVS Chief, Soft Tissue Surgery Section
Department of Clinical Sciences of Companion Animals
Faculty of Veterinary Medicine, Utrecht University
Utrecht, The Netherlands
j.kirpensteijn@vet.uu.nl

Textbook of Small Animal Orthopaedics, C. D. Newton and D. M. Nunamaker (Eds.)
Publisher: International Veterinary Information Service (www.ivis.org)
Ithaca, New York, USA

Malignant Bone Tumors in the Dog (1-Jan-1985) M. H. Goldschmidt and D. E. Thrall

Canine Cancer Awareness.org

Benign Bone Tumors in the Dog
Michael H. Goldschmidt and Donald E. Thrall