bubble_chart Overview

Malignant fibrous histiocytoma (MFH) mostly occurs in deep soft tissues and was first reported by O'Brien and Stout. Primary intraosseous MFH is very rare. In 1972, Feldman and Norman proposed classifying this tumor as an independent type of bone tumor. Previously, intraosseous MFH was often misdiagnosed as osteosarcoma, fibrosarcoma, giant cell tumor of bone, or metastatic bone cancer.

bubble_chart Pathological Changes

(1) Gross Findings: The tumors are all osteolytic and gray-white in color, accompanied by scattered hemorrhagic and necrotic foci, presenting a variegated appearance of gray-red or gray-brown. A few cases show cystic changes.

(2) Microscopic Findings: The tumor is composed of anaplastic histiocytes and fibroblasts, with occasional benign or malignant multinucleated giant cells and inflammatory cells visible. No calcification foci are present. The histiocytes are round or nearly round, with round or reniform nuclei, showing significant atypia, abundant cytoplasm, and phagocytic phenomena. Foam cells contain cellular debris and hemosiderin. The fibroblasts vary in density, arranged in a whorled or cartwheel pattern, with large oval cell bodies and markedly atypical nuclei. The multinucleated giant cells can be classified as benign or malignant. The former closely resemble osteoclasts or Touton giant cells, while the malignant ones are tumor giant cells.

bubble_chart Clinical Manifestations

Malignant fibrous histiocytoma is a rare disease. The age of onset is mostly middle-aged and elderly, with males slightly outnumbering females, at a ratio of approximately 10:8. The most common sites of occurrence are the metaphysis of the distal femur and proximal tibia. The most frequent symptoms are localized pain and swelling, with a slow onset that can range from several weeks to several months.

**X-ray findings** The lesion appears as a focal, radiolucent defect, often with well-defined margins, predominantly located in the metaphysis. Cortical destruction is frequently observed, with penetration into the soft tissues. There is no significant bone membrane reaction. The radiographic features resemble those of other primary or secondary malignant tumors and are nonspecific. Whole-body bone scans and CT examinations can help determine whether the tumor originates from the intramedullary or extraosseous region.

bubble_chart Treatment Measures

This tumor is highly malignant with a poor prognosis and an extremely low 5-year survival rate. In recent years, survival rates have improved with advancements in treatment methods. If complete surgical resection is performed along with long-term chemotherapy, the 5-year survival rate can increase to 57-67%. Radiation therapy is generally ineffective and may only be attempted for patients who are not candidates for surgery.