Malignant Fibro Histiocytoma (MFH)
This has become the most common malignant sarcoma of older adults. It tends to occur in the deep soft tissue of the extremities and the retroperitoneum. However, it has been described in nearly every organ of the body. Signs and symptoms relate directly to the location in which it arises. It is a diagnosis of exclusion; the burden of proof is upon the pathologist to do a battery of immunohistochemical studies to exclude other sarcomas such as rhabdomyosarcoma and liposarcoma. Several histologic variants are described (storiform-pleomorphic, myxoid, inflammatory, giant cell, and angiomatoid). In general, all of these tumors follow an aggressive course and will recur unless widely excised. Angiomatoid variants appear to be a distinct disease occurring in younger patients and having a more indolent course. Recently, many investigators have questioned the uniqueness of this tumor, indicating that many are actually pleomorphic tumor derived from muscle cells or even fat cells. The outline below highlights some of the current controversies.
MFH accounts for 20-24% of soft-tissue sarcomas, making it the most common soft-tissue sarcoma occurring in late adult life.
Distinct Clinical Features
Soft tissue MFH can arise in any part of the body but most commonly in the lower extremity, especially the thigh. Other common locations include the upper extremity and retroperitoneum. Patients often complain of a mass or lump that has arisen over a short period of time ranging from weeks to months. It is not uncommon for patients to report trauma to the affected area. For example, patients will state that they “ran into the corner of a table” and have had a thigh lump since. Trauma as far as we know does not cause MFH but rather the incident draws attention to the extremity. The mass does not usually cause any pain unless it is compressing a nearby nerve. Symptoms such as weight loss and fatigue are not typical but can present in patients with advanced disease. Retroperitoneal tumors can become quite large before they are detected as patients do not feel a mass per se but rather associated constitutional symptoms such as anorexia or increased abdominal pressure.
Biopsy confirms the diagnosis. Chemotherapy and surgical management are mainstays of treatment. Treatment is similar to that for osteosarcoma of bone, comprised of Adriamycin, methotrexate, cis-platin or ifosfamide. Limb sparing surgery is usually appropriate, with only patients with unresectable tumors requiring an amputation. Studies have shown a longer disease-free survival in patients that have a good response to neoadjuvant chemotherapy. There are reports as high as 94% disease-free survival in good responders versus 61% for poor responders. Radiation is rarely used, but may have a role in treatment of patients with micrometastic disease or unresectable tumors.