Understanding Fibrosarcomas in Dogs: A Guide for Pet Owners

Understanding Fibrosarcomas in Dogs: A Guide for Pet Owners

Fibrosarcomas in dogs are a type of malignant tumor arising from fibroblasts, the cells that form the connective tissue in the body. These tumors predominantly affect the skin and subcutaneous tissue but can also occur in bones, nasal cavities, and the mouth. This condition is a serious health concern, particularly in certain dog breeds and older dogs.

Causes of Fibrosarcomas

The exact cause of fibrosarcomas in dogs remains unclear, but a combination of genetic and environmental factors is believed to play a role. Chronic inflammation, exposure to radiation, trauma, and the presence of foreign bodies or orthopedic implants may contribute to the development of these tumors. In some cases, there is evidence suggesting a link between injection sites and tumor development.

Certain large dog breeds like Irish Setters, Irish Wolfhounds, Golden Retrievers, and Doberman Pinschers are more susceptible to fibrosarcomas. The average age of onset is around 10 years, but younger dogs can also be affected, often with a more aggressive form of the cancer.

Symptoms and Diagnosis

Symptoms of fibrosarcoma vary depending on the tumor's location and size. Common signs include:

  • A firm lump or bump on or under the skin, sometimes ulcerated or infected.
  • Swelling and pain in the affected area, leading to behavioral changes such as withdrawal or loss of appetite.
  • Lameness or difficulty moving if the leg is involved.
  • Nasal discharge, sneezing, or breathing difficulties if the nasal cavity is affected.
  • Oral discomfort, reluctance to eat, drooling, or bleeding from the mouth if the tumor is in the mouth.

Diagnosis typically starts with a physical examination, followed by X-rays, CT scans, and histopathological examination through fine needle aspiration (FNA) or tissue biopsy. Biopsies are preferred for a more accurate diagnosis and to determine the cancer's grade.

Progression and Treatment

Untreated fibrosarcomas can grow slowly, often becoming ulcerated and infected. They are locally invasive and can lead to bone destruction and fractures if they invade or originate within the bone. Metastasis occurs in a minority of cases, but high-grade tumors have a higher risk.

Treatment primarily involves surgery, aiming for wide and deep margins to reduce the chance of recurrence. However, complete removal is often challenging. In cases involving the nasal cavity, mouth, or leg bones, more extensive surgeries, including partial jawbone removal or amputation, may be necessary. Post-surgical histopathology helps determine the likelihood of recurrence or metastasis and whether additional therapies like radiation or chemotherapy are needed.

Aftercare and Prognosis

Post-treatment, it's crucial to monitor for signs of recurrence, especially since fibrosarcomas tend to recur in the same area. While metastasis is rare, proactive observation and regular veterinary check-ups are essential for early detection and intervention.

The prognosis for dogs with fibrosarcoma varies based on the tumor's location, grade, and how early it is detected and treated. With timely and appropriate treatment, many dogs can have favorable outcomes, even if the cancer is not entirely curable.


Fibrosarcomas in dogs are a significant health concern but understanding the signs, risks, and treatment options can help pet owners manage this condition effectively. Early detection and prompt veterinary care are key to providing the best possible outcomes for dogs with this type of cancer.

Tilbage til blog