Giant Cell Tumor of Bone There are numerous primary tumors of bone with giant cell oror macrophage activity seen within the tumor under the microscope.These include the aneurysmal bone cyst, chondroblastoma, solitarybone cyst, osteoid osteoma, osteoblastoma, fibrous dysplasia andosteogenic sarcoma, hemorrhagic type. Some pathologists classifythese tumors as variants of the true giant cell tumor making it almosta diagnosis of exclusion if none of the above diagnoses can beestablished histologically. The clinical entity known as the benigngiant cell tumor of bone is seen typically in young adult femalesbetween the ages of 20 and 40 years. It is less common in males. Thelesion is usually found in the ends of long bones, most commonlyabout the knee joint where 50% of the lesions will be seen. The nextmost common locations are the sacrum and distal radius. The otherepiphyseal tumor seen in children is the chondroblastoma that alsohas giant cell activity in the tumor. Even the so-called brown tumorof hyperparathyroidism has excessive macrophage activity but is a
pseudotumor induced by parathormone producing lesions such asparathyroid adenomas and secondary hyperparathyroidism seen inrenal failure disease. Currently most experts feel that the giant cell tumor is a low-grade,benign mesenchymal tumor with a fibro-osteoblastic stem cell with amolecular genetic defect similar to the stem cell of the osteosarcomabut with a greater degree of molecular genetic stability. The giant cellseen in this tumor is simply an immune response by the host in anattempt to remove the neoplastic fibro-osseous tissue. Giant celltumors account for between 5-10 per cent of all benign tumors of theskeletal system. They are usually associated with pain in the adjacentjoint involved, such as the knee joint, which may cause an effusion.radiographically, the lesion is very characteristic because of its purelylytic nature that can be very geographic in nature, located in theepiphyseal-metaphyseal location of a long bone, frequently coming indirect contact with the subchondral bone of the adjacent joint. In moreaggressive cases, the lesion can break through the adjacent metaphyseal
cortex and gain access to the subperiosteal space and take on theappearance of a more malignant process, such as a hemorrhagicosteosarcoma. Even though this condition is considered benign with a very lowmitotic index seen in the stromal cells, one or two per cent of thetumors can metastasize to the lung as a benign process. There is anexcellent prognosis for cure with simple surgical resection in 80% ofthe cases. Treatment usually consists of an aggressive curettementof the tumor followed by a packing of the defect with either bonegraft, in smaller lesions, or more typically with bone cement inlarger lesions which gives a better chance of a permanent cure withabout a 5 to 10% recurrence rate with the cementation technique. Inmore aggressive lesions located in the sacrum or anterior portionof the spinal column, surgical resection is very difficult because ofthe adjacent nerve roots or spinal cord, in which case occasionallylocal radiation is used. However, in about 5% of cases, this canconvert the tumor into a high-grade tumor sarcoma at a much later
date. The tumor also has the potential for spontaneous conversionto a high grade tumor, such as an osteosarcoma or a malignantfibrous histiocytoma, in about 1% of cases. Giant cell tumors that have a local recurrence have a greaterpotential for pulmonary metastasis, running as high as 6% and, forthis reason, chest x-rays should be obtained periodically for aperiod of approximately three years after the primary treatment ofthe tumor.
CLASSICCase #20723 year female withGCT proximal tibia
Later she developed arecurrence in the tibiawhich led to an AK ampand then developed thepath fracture in femoralstump seen here thru yetanother multifocal GCTLater on she developedbenign pulmonary metsand died 6 mos later whileon chemotherapy