BCOR‑CCNB3 sarcoma arising in the proximal tibia: A case report

Abstract

BCL6 corepressor-cyclin B3 (BCOR-CCNB3) fusion sarcoma was classified as an emerging subgroup of undifferentiated small round cell sarcoma in 2020. The incidence of BCOR-CCNB3 fusion sarcoma is reportedly 1.5-14% among undifferentiated unclassified sarcomas, representing a rare entity among primary malignant bone tumors. The present study reports a case of BCOR-CCNB3 fusion sarcoma in the proximal tibia of a boy. A 12-year-old boy presented with a 6-month history of knee pain and a slowly growing mass in the anteromedial aspect of the left proximal tibia. Plain radiography and computed tomography of the knee demonstrated a lytic lesion with cortical destruction of the proximal tibia. Magnetic resonance imaging showed the bone tumor expanding into soft tissue with almost homogeneous hypointensity on T1-weighted imaging and slightly hyperintensity on T2-weighted imaging. On histopathological evaluation, the tumor comprised a proliferation of small, round to ovoid-shaped mesenchymal cells without osteoid formation. Histopathologically, BCOR-CCNB3 sarcoma of bone was finally diagnosed based on immunohistochemical staining and additional molecular analyses. The patient underwent bone tumor resection followed by pre-and post-operative chemotherapy according to a Ewing sarcoma protocol. The patient showed no evidence of local recurrence or distant metastasis at 12 months after completion of adjuvant chemotherapy. We present herein an additional case of BCOR-CCNB3 sarcoma of the proximal tibia, and review the relevant literature on BCOR-CCNB3 sarcoma of bone.

A Rare Case of Nasal Sarcoma with BCOR Internal Tandem Duplication Showing Complete Pathologic Response to the VDC-IE Chemotherapy Protocol

“…In contrast to CIC::DUX4 rearranged round cell sarcomas, BCOR::CCNB3 rearranged sarcomas are more inclined to occur in the bone, whereas CIC rearrangement sarcomas tend to develop in soft tissues and to follow a more aggressive trajectory. Additionally, BCOR::CCNB3 sarcomas display a higher occurrence in males, which is not observed in CIC-rearranged sarcomas [1][2][3][4].…”

“…However, there has been no consensus regarding the optimal regime owing to the lack of clinical trials. The use of the Ewing sarcoma regimens (VDC-IE, VIDE) has been commonly reported [ 1 , 3 , 4 , 7 , 8 , 14 , 15 ]. However, other utilized regimens included ifosfamide and doxorubicin [ 1 , 2 , 7 ] and osteosarcoma regimens such as platinum and anthracycline combinations and methotrexate [ 2 , 4 , 14 ].…”

“…In their publication, they identified a novel gene fusion, namely, BCOR::CCNB3. Since then, there has been a growing body of literature discussing this disease entity [2][3][4][5]. Nevertheless, most of the current evidence is based on case reports and series that include small number of patients [3,4].…”

“…BCOR-rearranged round cell sarcomas are extremely rare tumors, with a more favorable outcome compared to CIC::-DUX4 round cell sarcoma. We reviewed the literature and identified a total of 166 reported cases of BCOR-rearranged sarcoma[1][2][3][4][6][7][8][9][10][11][12][13][14][15][16][17]. Molecular alterations included BCOR::CCNB3 in 131 patients (79%), other BCOR fusions…”