Malignant Fibrous Histiocytoma Health Article

Definition

Malignant fibrous histiocytoma (MFH), although rare, is the most common abnormal growth of soft tissue (sarcoma) in adults.

Description

MFH occurs as a painless mass most commonly in the skin, arms, legs, kidneys, or the pancreas. More rarely MFH may occur in the bones, heart, breasts, or inside the skull.

When MFHs spread (metastasize) to other organs, the most common site is the lung, but metastasis to local lymph nodes and to bone have also been reported.

MFHs tend to be slow growing and slow to metastasize.

Local recurrence of MFH after surgery to remove the initial tumor is common because MFHs grow along the fat layers that separate different layers of soft tissue. Often, an MFH is not completely removed because it has crossed, undetected, from one fat layer to another neighboring layer.

Demographics

MFHs are diagnosed in six of every one million people each year. MFHs can occur in people of any age, but they are extremely rare in children.

MFHs occur in a slightly higher frequency in Caucasians than in people of African descent or Asians. No relationship of MFHs appear to exist to any geographic region. Males are affected in slightly higher numbers than are females.

MFHs of the skin are seen almost exclusively in sun-exposed areas of the skin in elderly patients.

People affected with certain genetic diseases, such as neurofibromatosis, have a higher incidence of MFHs than unaffected people.

MFHs of the bone are seen almost exclusively in people who have a pre-existing skeletal disorder such as Paget disease or fibrous dysplasia of bone.

Causes and symptoms

The cause, or causes, of MFHs are not known. An elevated risk for the development of MFHs has been linked to the chemical phenoxyacetic acid found in herbicides; to clorphenols found in wood preservatives; and to exposure to asbestos. People who have been exposed to high doses of radiation are also more prone to develop MFHs than the remainder of the population. Research is ongoing to determine if there is a genetic cause of MFHs.

The only direct symptom of MFHs is the presence of an abnormal mass, but some patients may also experience:

• abnormally high levels of a certain type of white blood cells (eosinophils) in the blood
• low blood sugar (hypoglycemia)
• fever
• abnormal liver function tests