Clinical and cytogenetic aspects of giant cell tumor of the sternum

Abstract

Giant cell tumor (GCT) is a benign, locally aggressive bone tumor that usually affects the metaphysis and the epiphysis of long tubular bones. It is most frequently located around the knee. It is commonly diagnosed in patients between the ages of 20 and 45 years.1 GCT metastasizes merely to the lungs in 2% of cases with unpredictable behavior. The sternum is infrequently affected by bone tumors. Although uncommon, malignant neoplasms, such as chondrosarcoma, osteosarcoma, myeloma, and lymphoma, are most likely to occur in this location.2 GCT of the sternum is an even rarer condition,3,4 and only seven cases are well documented in the literature.5-11 The present article describes the clinical and cytogenetic aspects of an additional case of GCT of the sternum occurring in a young male and includes a discussion of the surgical treatment. Case Report A 32-year-old man presented with a sternal mass that had shown progressive growth toward the suprasternal notch over the previous ten months. He complained of local pain that radiated to the cervical region and shoulders. Physical examination showed a bony, tender, six cm large mass of the manubrium (Figure 1A). The patient's pain was increased by palpation and elevation of his arms. Figure 1 A) Clinical aspect before and after surgery; B) intraoperative aspect after sternum resection; C) intraoperative aspect after reconstruction; and D) CT sagittal reconstruction showing anterior focal cortical bone destruction and soft tissue extension ... Plain radiographs showed an expansile osteolytic lesion of the sternum. Computed tomography (CT) and magnetic resonance imaging (MRI) demonstrated focal cortical bone destruction, soft tissue extension and subchondral extension in relation to the sternoclavicular joints. CT images confirmed the osteolytic nature of the tumor and the absence of internal mineralization. Post-contrast CT and MRI demonstrated small foci that lacked the enhancement consistent with cystic or hemorrhagic areas. MRI showed that the lesion was of intermediate signal intensity on T1- and T2-weighted images and included additional areas of high signal intensity on the T2-weighted images (Figure 1D-E). Histology from a prior biopsy performed at an outside institution revealed a benign tumor composed of multinucleated giant cells compatible with a GCT or a brown tumor of hyperparathyroidism. Laboratory evaluation revealed normal levels of calcium (1.25 MMol/l) and parathyroid hormone (21 PG/ml), making the diagnosis of a brown tumor highly unlikely. The patient underwent resection of the manubrium with wide margins and post-resection reconstruction with GORE® DUALMESH® PLUS Biomaterial (W. L. Gore & Associates, Inc., Flagstaff, USA) mesh fixed with polyester separated stitches. Both the clavicles and the first ribs were fixed to the mesh. Thoracic inspection showed no mediastinal or lung nodules. Disarticulation of the body-manubrium joint was uneventful. A bilateral pectoralis major flap covered the mesh and allowed skin closure (Figure 1B-C). Histological analysis of the resected specimen revealed the presence of multinucleated giant cells, mononucleated small cells and spindle cells with elongated nuclei without atypias. Occasionally, more than 100 nuclei could be perceived in the giant cells, a typical characteristic of GCT (Figure 2A). Figure 2 A-D) Histological aspect of the lesion showing a triphasic aspect with giant, mononuclear and fusiform cells (B), bone (C) and soft tissue (D) invasion of the tumor, and cystic formations (H&E, A - 400×, B - 200×, C - 100×, ... The tumor growth had induced extensive bone erosion and focally infiltrated adjacent soft tissues (Figure 2B-C). Blood-filled dilated spaces were seen, suggesting an association with an aneurysmal bone cyst (Figure 2D). Less than one typical mitotic figure was seen per ten high power fields. Atypical mitosis, vascular invasion, and tumor necrosis were not detected. To allow for cytogenetic studies, a fresh GCT sample (adjacent to areas of the tumor verified by frozen section) was aseptically collected in the operating room and processed as previously described.12 Cytogenetic analysis was performed on 30 metaphases and showed a complex complement characterized by the presence of numerous marker chromosomes. The karyotype was denoted as 51, XY, -7, +9, del(10)(q23), add(11)(p15)x2, -15, add(18)(q23), +mar1, +mar2×2, +mar3, +mar4, +mar5 (Figure 2E).