In 1942, Jaffe et al. considered it to be a tumor and separated it from the group of giant cell tumors, while in 1945 Hatcher pointed out that nonossifying fibroma, essentially a tumor-like lesion, is also known as fibrous cortical defect disease of the epiphysis, but nowadays it is considered to be pathologically indistinguishable from fibrous histiocytoma. It is difficult to distinguish this lesion from fibrous histiocytoma. The lesions contain multinucleated giant cells and are more common in the epiphyseal cortex of long tubular bones. Etiology The tumor is well-defined, eccentric, firm or tough, and yellow or dark brown in color on the surface. It is composed of yellow and maroon fibrous connective tissue containing lipid-like material. The tumor tissue is mixed with brownish-yellow areas, with localized thinning and swelling of the bone cortex, clearly bounded by normal bone and surrounded by sclerotic bone or fibrous bone. The adjacent bone cortex is intact unless a pathological fracture has occurred. If the tumor consists of multiple lesions, it may be lobulated. There is usually no periosteal reaction. Microscopically, the histology is characterized by spindle-shaped fibroblastic hyperplasia in a swirling or matted arrangement with a few collagen fibers and fibroblasts. Reticular fibers are generally abundant. There is sometimes hemorrhage and iron-containing heme deposits in the interstitium, the latter seen in spindle-shaped cells and multinucleated giant cells. Focal clusters of foam cells are prominent, and the tissue cells that phagocytose lipids and iron-containing heme are foam cells transformed from fibroblasts. 1/3 of cases have foam cells. However, in some cases, fibrous tissues and cells are more common and foam cells are less common. Non-ossifying fibromas that are about to degenerate have thickened collagen bundles and resemble fibromas. The third component is multinucleated giant cells, usually with 3 to 10 nuclei, a few cells are large with more nuclei, scattered in the tissues, sparsely distributed and small in shape, unlike giant cells in giant cell tumors, and lymphocytes and plasma cells can be seen between the tissues. There is no osteogenic activity in the tumor, which can be distinguished from fibrous proliferation disorder. The margins may produce reactive osteosclerosis by distending expansion of the tumor. The histologic picture is consistent with a benign fibrous histiocytoma. These features suggest that this tumor is of fibrous histiocytic origin. Treatment is generally surgical with debridement and bone grafting, and segmental resection may be considered if necessary, if the tumor is in the fibula. After complete removal or resection, the recurrence rate is very low. Pathological changes: 1. The defective fibrous bone cortex at the epiphysis is composed of tough fibrous connective tissue. The tumor is surrounded by a thin shell of sclerotic bone tissue. Microscopic examination: a large number of fibroblasts arranged in a swirling pattern can be seen, and a few scattered giant cells and foam cells can be seen. Many cells contain iron-containing heme granules, but no matter how abundant the cells are, there is generally no osteogenesis within the tumor cells, which is characteristic of this disease. Reactive hyperplasia may occur in the adjacent bone tissue. Clinical manifestations The disease occurs in children and adolescents, with no significant differences between the two sexes. The lesions are most commonly found in the long tubular bones of the lower limbs, such as the tibia, femur and fibula, but are rarely found in other areas, occasionally in the skeleton and sacroiliac joints, or in the ulna and humerus of the upper limbs. The lesions are usually located at the upper and lower ends of the diaphysis and grow in an expansive fashion, at a distance of 2.5 to 5.0 cm from the epiphyseal cartilage. The absence of specific clinical symptoms aids in the diagnosis of the disease, and the lesions are usually found on x-ray. They develop slowly, potentially, and take several years to develop before localized pain and swelling, mainly in the ankle, knee, and wrist joints, and are often mistaken for being caused by minor trauma. Occasionally, it can be detected after a pathological fracture. The lesion is eccentric and well-defined, starting not far from the epiphyseal plate and moving toward the bone stem as the bone grows. The tumor is usually found in the upper tibia and lower femur. The lesion is lobulated and lax, oval in shape, and can be 4-7 cm in diameter. Differential diagnosis 1. Giant cell tumor of bone: the connective tissue cells are larger and the giant cells are also larger and more numerous, whereas the opposite is true for non-ossifying fibromas. The disease is characterized by an age of 8 to 20 years, a predominantly epiphyseal and diaphyseal site, the possibility of self-healing, and a low recurrence rate. Yellow granuloma: Since this disease can absorb fat and become foam cells during the healing stage, it is suspected to be yellow granuloma, so it should be noted. 2.Solitary fibrous abnormal proliferation disease Especially, cystic changes are rare. It occurs mostly in the proximal epiphysis of long tubular bones and has no obvious clinical symptoms. X-ray shows limited osteolytic bone destruction in the medullary cavity, which is frosted glass-like, with irregular bone trabeculae or calcification, and no obvious osteosclerosis at the edge. Microscopically, fibrous tissue and metaplastic bone are seen. Prevention of recurrence The disease requires attention in eating, otherwise it is easy to relapse, there are chicken, eggs, seafood, lamb, beef, rabbit, lobster, pork eat less.