Kiyong Na’s research while affiliated with Kyung Hee University and other places

Osteochondroma is a benign, cartilaginous, outgrowing neoplasm arising from the surface of the long bone; it consists of cartilage-capped bony overgrowth with extension of native bone marrow. The most common primary bone tumor, it is approximately 1.5 times more common in males than in females. About half the cases occur in the second decade of life. There is predilection for the distal femur, followed by the proximal humerus and proximal tibia. Roentgenograms show a pedunculated or sessile protuberance from the long bone metaphysis. The cortex of the host bone flares out into the osteochondroma cortex. The cartilage cap is covered by a thin periosteal membrane. The limit between the cartilage cap and the underlying cancellous bone shows endochondral ossification, closely mimicking a normal epiphyseal plate. Treatment is surgical excision with the entire cartilage cap.

Chondroblastoma is a benign cartilage-forming neoplasm occurring in the epiphyses of immature long bones. It is more common in males. The peak incidence is between 10 and 25 years of age. Typically, chondroblastoma occurs in the epiphyses of the long bones. More than 75% of cases develop in the epiphyseal and epimetaphyseal region of the distal and proximal femur, proximal tibia, or proximal humerus. Radiologically, chondroblastoma is usually located in the medullary portion and arises at either the epiphysis or apophysis of the long tubular bone. Extension to the metaphysis sometimes can be seen. The lesion consists of well-defined, geographic bone destruction with either a spherical or oval shape. There are amorphous calcific foci within the lesion. Histologically, the basic cells are chondroblasts. There are randomly distributed multinucleated giant cells. Immature chondroid matrix is typically present; it appears as variably sized nodules composed of light-staining, amorphous, bluish to eosinophilic material surrounded by chondroblasts. Most chondroblastomas are appropriately treated by curettage.

Periosteal chondroma is a benign hyaline cartilage tumor of the bone surface, which develops from the periosteum. Males are more commonly affected than females. Patients are usually 10–30 years of age. The proximal humerus is the single most frequently affected site, followed by the distal femur. On radiographs, periosteal chondromas appear as one or more cortically situated, lobulated soft-tissue masses with erosion or cortical saucerization. There may be associated medullary sclerosis and periostitis. Histologically, periosteal chondromas show characteristic lobules of hyaline cartilage. Treatment is conservative surgical excision.

Enchondroma is a common, benign intramedullary neoplasm composed of mature hyaline cartilage. Enchondromas account for 10–25% of all benign bone tumors. It is most common from the second to the sixth decades with a peak in the fourth and fifth decades, and is more frequent in females. It is most frequently found on the small tubular bones of the hands. Among the long tubular bones, enchondroma occurs more frequently in the proximal humerus and proximal and distal femur and tibia. Histological features vary according to the location of the lesion, so it is very important to consider the location of the lesion together with the radiological findings and clinical features. Enchondromas are composed of mature hyaline cartilage arranged in lobules. Cartilaginous lobules are surrounded by normal bone marrow. When treatment is needed, simple curettage is the appropriate treatment.

Phosphaturic mesenchymal tumor (PMT) is a neoplasm that produces a phosphaturic substance, fibroblast growth factor-23 (FGF23), causing systemic phosphate depletion and leading to oncogenic osteomalacia. Sites of occurrence are the soft tissue and bone, with almost half of the cases in the lower extremities. A long history of osteomalacia, bone pain, and fractures is usually present. Renal phosphate wasting and elevated serum levels of FGF23 are found. Radiologically, the tumor may present a varied appearance. Histologically, three variants are seen: osteoblastoma-like, non-ossifying fibroma-like, and mixed connective tissue variant (PMTMCT), the commonest. This is characterized by a hemangiopericytoma-like tissue pattern and areas of matrix with peculiar calcifications. FGF23 may be identified within PMT cells by RT-PCR and immunohistochemistry. Osteomalacia may be cured once the tumor is discovered and resected. Exceptional cases of malignant PMTs may behave aggressively.

Chondromyxoid fibroma is a benign tumor composed of spindle or stellate cells forming lobules, with abundant myxoid and/or chondroid intercellular material. There is a male predominance. More than half of cases develop in the second and third decades of life. Most cases occur in the metaphysis of tubular bones of the lower extremity. Approximately one third of cases are diagnosed around the knee joint; the proximal tibial metaphysis is the most common site of involvement, followed by the distal femoral metaphysis. Rarely, cases involve flat bones. A sharply circumscribed, radiolucent lesion with an elongated shape is seen on radiographs. Cortical expansion, exuberant endosteal sclerosis, and coarse trabeculation can be seen. The primary and preferable treatment should be en bloc resection.

Multiple enchondromatosis (Ollier’s disease) is a rare, nonhereditary developmental abnormality involving defective endochondral ossification. It is characterized by multiple intraosseous and subperiosteal cartilaginous tumors, ranging in size from microscopic foci to bulky masses. The skeleton is most frequently affected unilaterally, but bilateral involvement is also observed. The association of enchondromatosis with multiple hemangiomas of soft tissue was reported in 1881 by Maffucci (18 years before Ollier), and this clinical presentation is generally referred to as “Maffucci’s syndrome.”

Multiple osteochondromatosis is a familial disease characterized by multiple osteochondromas, defect in metaphyseal remodeling, and asymmetric longitudinal growth retardation. There is a greater incidence in males than in females (7:3). It is often first discovered at a younger age than solitary osteochondromas. There is a predilection for the metaphyseal regions around the knee, hip, and shoulder joints. Radiologically, the individual lesions are similar to those of the solitary form, and they have the same gross and microscopic appearance. The development of secondary malignancy varies from 5% to 25%. Treatment should be considered to correct deformities or functional disturbances.

In skeletal pathology diagnosis, most tumors and tumorlike conditions can be diagnosed with routine hematoxylin and eosin (H&E) stain, but sometimes this basic technique can be insufficient. Histochemical methods evaluate the state of the ossification process and intracellular activated enzymes (PAS, mucin stain, Congo red, von Kossa, etc.). Electron microscopy, flow cytometry, and histomorphometry have limited diagnostic uses. Immunohistochemical staining has been a helpful aid, especially in the diagnosis of round-cell tumors, metastatic disease, Langerhans cell histiocytosis, and vascular tumors. Karyotyping, molecular cytogenetic techniques such as FISH, and molecular techniques like blotting, PCR, and others have limited but effective application in the diagnosis of some specific bone tumors.

Grading is applied only to malignant tumors. Usually, a scale of 1–3 is used to grade malignant tumors, based on their histological resemblance to “normal counterparts.” Conventional osteosarcomas are high-grade tumors. Chondrosarcoma is graded on a scale of 1–3. Ewing’s sarcoma and mesenchymal chondrosarcoma are always regarded as high-grade tumors. Malignant lymphoma, myeloma, chordoma, and adamantinoma are not graded because grading has not been proved to correlate with clinical behavior.