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Tumor template based on A Clinical Guide to Primary Bone Tumors. Levesque et al.
Tumor biology and incidence
Malignant fibrous histiocytoma (MFH) is a tumor of mesenchymal origin that exhibits a heterogeneous histology of spindle cells in a characteristic storiform or "starry night" pattern. The most common soft tissue malignancy in adults, MFH comprises 1 to 5% of all primary bone tumors. The World Health Organization has recently replaced the term MFH with undifferentiated high grade pleiomorphic sarcoma. MFH of bone can also arise as a secondary sarcoma in patients with previous bone infarcts, Paget's disease, or irradiated bone.
Age
Median age range 40 to 52 years old
In radiation-induced MFH, the median age range is 50 years old.
Gender
Male: Female ratio is approximately 3:2
Presentation
Patients present with a complaint of localized pain, swelling, and a possible mass. The complaints may be of several months duration. Up to 25% of patients present with a pathologic fracture. In some cases, serum alkaline phosphatase may be slightly elevated.
Physical findings
Site
Close to 75% of MFH lesions occur at the ends of long bones. Fifty percent of the lesions arise about the knee joint, favoring metaphyseal bone. The lesion will extend into the epiphysis or diaphysis, and rarely is there isolated diaphyseal involvement (<10%). Most commonly found in femur (45%), tibia (10%), pelvis (10%), and humerus (10%). These lesions are rarely found in the hands and feet. Less common areas include the skull, facial bones, ribs, fibular, spine, scapula and clavicle.
Tumor effect on bone
MFH has nonspecific radiographic images, but are consistent with malignancy. An eccentric "moth eaten" lesion in the metaphysis or meta-diaphyseal region is common. There is little periosteal reaction and no evidence of ossification or mineralization.
Cortex
Cortical destruction and soft tissue extension are characteristic.
Soft tissue mass
Grossly, MFH of bone is tannish-yellow color with fleshy areas. The degree of rubbery or softness varies depending on the level of necrosis and fibrosis. Hemmorrhagic and necrotic areas can be present variably, with larger areas more suspicious for high grade malignancy.
Bone scan
MFH of bone is positive on bone scan.
CT Scan
A useful modality to assess in three-dimensional fashion the amount of bone destruction.
MRI
A useful modality to delineate the intra- and extra-osseous components of the mass.
Differential Diagnosis
Osteosarcoma
Fibrosarcoma
Metastatic disease with spindle features
Melanoma
Primary Leiomyosarcoma
Synovial Sarcoma of Bone
Dedifferentiated component of dedifferentiated chondrosarcoma
Natural history
Five-year survival rates of 50 to 70% with chemotherapy and surgical management. Secondary MFH patients have a poorer prognosis.
Pathology
Storiform or "starry night" pattern of spindle cells and pleomorphic cells. The area is hypercellular, high grade, with 5 to 10 mitotic figures per high powered field. Hypercellular areas are characterized by scant matrix. Hypocellular areas have an abundant fibrous matrix. The matrix can be very eosinophilic.
Diagnosis and treatment
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.
A 1997 meta-analysis showed that chemotherapy had little effect on the overall recurrence-free interval (10% improvement), local recurrence-free interval (6% improvement), distant recurrence-free interval (10%), and in overall survival (4%).
Metastatic disease can occur with MFH, as with other tumors. Most common sites of metastatic lesions are lung and other bones. The five-year survival rate in this patient group is 10% if treated with aggressive chemotherapy and surgical resection.
Complications
See above for metastatic disease and survival rates.
Recommended Reading
Bullough P. Orthopaedic Pathology, 4th Ed. London, UK: Mosby, 2004.
Sarcoma meta-analysis collaboration. Adjuvant of chemotherapy for localized resectable soft-tissue sarcoma of adults:meta-analysis of individual data. Lancet 1997;350:1647-54.
Wittig JC and Villalobos CE: Other Skeletal Sarcomas, in Schwartz HS. Orthopaedic Knowledge Update: Musculoskeletal Tumors 2. Rosemont, IL: American Academy of Orthopedic Surgeons, 2007, pp 197-198.
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