Bone Cancer (Fibrosarcoma) in Cats

4 min read

Fibrosarcoma of the Bone in Cats

Fibrosarcoma is normally a tumor that originates in the soft tissue, a result of abnormal division of fibroblast cells – the cells that are most prevalent in the connective tissue of the body. In some rare cases, a fibrosarcoma tumor originates in the bone, weakening the structure of the bone, and possibly leading to fractures, and even amputation of the limb. In most cases fibrosarcoma of the bone is benign and non-metastasizing, but there are cases where the tumor is malignant and metastasizes throughout the body, into the organs, lymph nodes and skin.

Clinically, fibrosarcoma of the bone is similar to osteosarcoma, a more common form of bone cancer. The main differences are in the make-up of the tumors. Where an osteosarcoma is made up of bone material, a fibrosarcoma is made up of fibrous collagen material. Fibrosarcoma is confirmed when a biopsy of the tumor shows no production of bone material. The rapidly dividing nature of a sarcoma is the real danger, as it invades and threatens the stability of the bone. In general, tumors of the bone are benign, and are frequently misdiagnosed as cysts and muscular problems.

Symptoms and Types

  • Loss of motion, inability to walk
  • Mass can be palpated (examined by touch) at the affected bone
  • Swelling at the site
  • Pain when area is touched
  • Fractures of the bone without other evidence of trauma


The exact cause for a sarcoma of the bone is still unknown.


You will need to give a thorough history of your cat's health, onset of symptoms, and possible incidents that might have led to this condition, such as any accidents or illnesses. Standard laboratory tests include urinalysis, a complete blood count, and a chemical blood profile. The presence of higher than normal white blood cells can indicate that the body is warding off a diseased condition, and the other tests will show whether the organs are functioning well, but often, laboratory tests will return as normal. Because of the relative rarity of a fibrosarcoma of the bone, unless an x-ray image is taken it may be diagnosed as a cyst or a swelling in the muscle. Therefore, an x-ray examination will be an important factor in the definite diagnosis. X-rays will also help to diagnose the exact location of the primary tumor, as well as detecting whether there has been metastasis to other parts of body. A computed tomography (CT) scan is another useful diagnostic viewing tool that may help in determining the extent of problem.

For a more conclusive diagnosis, a biopsy of the tumor will need to be taken for analysis. A biopsy of the bone is a more invasive procedure than most, but this is the only way to confirm whether a tumor is benign or malignant. Your cat will need to be anesthetized for this procedure.


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