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

Diagnosis

Prior to removal, MFHs are extremely difficult to distinguish from the other forms of soft tissue sarcoma. The definitive diagnosis of MFH usually occurs after a tumor has been surgically removed. This diagnosis is accomplished by conducting microscopic examinations on the tumor.

Treatment team

Treatment for MFHs is mostly surgical or observational. Surgeries to remove MFHs are generally performed by orthopedic surgeons. MFHs rarely require any chemotherapies or radiation therapies, however, when these treatments are called for they are directed by a medical oncologist and administered by health care personnel who specialize in these fields.

Clinical staging, treatments, and prognosis

MFHs are divided into three grades based on the appearance of the tissue within the tumor. Low grade tumors may closely resemble the surrounding normal tissue. Intermediate and high grade tumors may have little resemblance to normal tissue.

Additionally, MFHs are divided into two clinical stages based on their size. Stage one MFHs are those tumors that are under 5 centimeters (2 inches) in diameter. Stage two MFHs are those tumors larger than 5 centimeters (2 inches) in diameter.

A treatment plan is determined after the grade and stage of the tumor has been established. High and intermediate grade tumors generally, regardless of the stage, are surgically removed. Low grade, stage one, tumors may be observed for development to a higher grade or stage rather than removed if it is determined that the risks of anesthetic and surgery outweigh the risk of the tumor to the individual patient.

Stage one MFHs are generally removed by wide local excision. This technique involves the surgical removal of the tumor and an area of healthy surrounding tissue that is approximately the same size as the tumor itself.

Stage two MFHs require wide surgical excision with the removal of wider margins of healthy tissue than those margins removed in the excision of smaller tumors. In some instances, stage two MFHs may require amputation.

Post-operative treatment of MFH patients may include chemotherapy or radiation therapy, especially in cases of MFH of the bones and in cases of metastasis to the lungs.

In cases of large MFHs, the patient may undergo radiation treatments prior to surgery in an attempt to shrink the size of the tumor prior to excision.

As of 2000, overall survival from MFH was approximately 75% 5-year disease-free survival. The prognosis is generally poorer if:

• the disease has metastasized to the lungs or bones
• complete tumor removal is not accomplished, or is not possible
• the patient is of an advanced age
• the tumor is large
• the location of the tumor is somewhere other than the arms or legs
• the tumor is located deep in the body, rather than superficially

Alternative and complementary therapies

There are no effective alternative treatments for MFHs other than surgical removal with or without chemotherapy or radiation treatments.