A malignant fibrous histiocytoma is a type of cancerous tumor that can originate in either bone or, most often, in the soft tissues that connect, support or surround organs and other body structures.

While it is among the most common types of soft tissue tumors found in adults, it is rarely found in children, making up only a tiny percentage of all soft tissue sarcomas, which as a group account for only 1 percent of new cancer cases in children each year.

Malignant fibrous histiocytoma is a painless mass that most often occurs in the extremities, although it can occur anywhere in the body. The condition most commonly spreads (metastisizes) to the lungs, but can also invade the lymph nodes and bone.

The exact cause of malignant fibrous histiocytoma is not entirely understood, however, studies have indicated that genetic alterations may play a role. Scientists are investigating the role of an associated genetic abnormality on the short arm of chromosome 19 that may give rise to this disease. It is known that malignant fibrous histiocytoma originates in primitive mesenchymal cells (undifferentiated cells that give rise to such structures as connective tissues, blood, lymphatics, bone and cartilage.)

The disease has also been linked to radiation treatment for breast cancer, retinoblastoma and Hodgkin's Disease. A malignant fibrous histiocytoma originating in the bone has been linked to pre-existing abnormalities such as Paget's disease or fibrous dysplasia of the bone.

Because malignant fibrous histiocytomas usually affect tissue that is elastic and easily moved, a tumor may exist a long time before being discovered, growing large, and pushing around surrounding tissue. The following are the most common symptoms of malignant fibrous histiocytomas. However, each child may experience symptoms differently. The symptoms vary greatly depending on size, location and spread of the tumor. Symptoms may include:

• A painless swelling or lump
• Pain or soreness caused by supressed nerves or muscles
• Limping or other difficulty using legs, arms, feet or hands

The symptoms of malignant fibrous histiocytoma may resemble other conditions or medical problems. Always consult your child's physician for a diagnosis.