Fibrosarcoma is a rare, malignant (cancerous) type of soft tissue sarcoma that occurs most commonly in infants and young children under 5 years of age and in patients 10 to 15 years old.

Like other sarcomas, fibrosarcoma occurs wherever fibrous tissues are found, and involves the extremities and deeper structures of the body. This type of cancer most commonly affects the limbs and the trunk of the body, but it can occur anywhere.

The symptoms depend on the area of the body where the tumor is located but usually include a swelling or lump.