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WHO Classification of Tumours
Malignant fibrous histiocytoma
Bone


Definition

Malignant fibrous histiocytoma (MFH) is a pleomorphic sarcoma characterized by the presence of fibrohistiocytic cells and spindle cells arranged in a storiform pattern. According to the 2003 WHO Classification
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Fletcher CDM, Unni KK, Mertens F (Eds.)
World Health Organization Classification of Tumours. Pathology and Genetics of Tumours of Soft Tissue and Bone.
3rd Edition
IARC Press: Lyon 2002



, this term is now used as a diagnosis of exclusion for sarcomas composed largely of myofibroblasts or undifferentiated mesenchymal cells and is synonymous with undifferentiated high grade pleomorphic sarcoma.

Primary malignant histiocytoma of bone predominantly arises in the metaphyseal regions of the long bones of the lower extremities, particularly the femur (30-45%), followed by tibia and humerus. The tumour is osteolytic and usually destroys the cortex; soft tissue extension is common. The margins are irregular and ill defined. In addition to the characteristic mixed population of spindle, histiocytoid and pleomorphic cells, varying amounts of multinucleated osteoclast-type giant cells, foamy cells and chronic inflammatory cells can be found within the lesion. The characteristic features of MFH are very similar to those of fibrosarcoma , and distinction between the two tumours can be arbitrary.
MFH of bone is a relatively rare tumour which affects adults and shows a predilection for males. MFH is a highly malignant neoplasm; most tumours are high grade tumours. Metastasis is frequent, particularly to the lungs(45-50%). The recommended treatment is wide surgical excision; preoperative chemotherapy is indicated in patients with histologically high grade lesions. Favourable prognostic factors are younger age at manifestation (<40 years), adequate surgical margins and histological low grade

Click for details
Fletcher CDM, Unni KK, Mertens F (Eds.)
World Health Organization Classification of Tumours. Pathology and Genetics of Tumours of Soft Tissue and Bone.
3rd Edition
IARC Press: Lyon 2002



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