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Case Reports
. 2025 Aug 8;17(8):e89654.
doi: 10.7759/cureus.89654. eCollection 2025 Aug.

BCOR::CCNB3 Sarcoma of the Thigh: A Rare Case

Abdul Moiz Khan  1 , Saliq Naeem  2 , Amna Ehtisham  1 , Rehan Ali  1 , Hamais Murtaza  1
Affiliations
Case Reports

BCOR::CCNB3 Sarcoma of the Thigh: A Rare Case

Abdul Moiz Khan et al. Cureus. .

Abstract

BCOR-rearranged sarcoma is a rare mesenchymal tumor and a recognized subtype of undifferentiated small round-cell sarcoma. It shares morphological similarities with other round-cell sarcomas but is distinguished by a unique molecular hallmark that differentiates it from Ewing sarcoma. These tumors primarily arise in bones and soft tissues. This case report details the case of an 11-year-old female who developed swelling on the medial aspect of her right distal thigh. There was no history of trauma, surgery, or fracture. Clinically, the presentation initially suggested osteosarcoma. However, histopathological evaluation confirmed a diagnosis of BCOR-rearranged sarcoma. This case highlights the importance of considering BCOR-rearranged sarcoma in the differential diagnosis of pediatric bone and soft tissue tumors, as its clinical and radiological features can mimic more common malignancies like osteosarcoma. Early recognition and accurate molecular diagnosis are crucial for guiding appropriate treatment.

Keywords: bcor-ccnb3; clinical pathology; ewing-like sarcoma; immunohistochemistry(ihc); sarcoma soft tissue.

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Conflict of interest statement

Human subjects: Informed consent for treatment and open access publication was obtained or waived by all participants in this study. Conflicts of interest: In compliance with the ICMJE uniform disclosure form, all authors declare the following: Payment/services info: All authors have declared that no financial support was received from any organization for the submitted work. Financial relationships: All authors have declared that they have no financial relationships at present or within the previous three years with any organizations that might have an interest in the submitted work. Other relationships: All authors have declared that there are no other relationships or activities that could appear to have influenced the submitted work.

Figures

Figure 1
Figure 1. Partially circumscribed soft tissue swelling bulge is seen along the medial aspect of the left upper thigh. No soft tissue calcifications are seen.
Figure 2
Figure 2. Axial T2-weighted MRI showing a hyperintense, well-defined mass in the thigh with surrounding edema.
Figure 3
Figure 3. Microscopic images showing clusters of soft epithelioid to spindle cells (black arrow) arranged in nests and cords against a myxoid background (white arrow) (A) and scattered appreciable calcific flakes (blue arrow) (B).
Figure 4
Figure 4. Microscopic images of the tumor showing focal areas of clear cell change seen in some sections (A) and areas of necrosis (blue arrows) and hemorrhages (black arrows) (B).
Figure 5
Figure 5. Microscopic images showing CD99 diffusely positive on immunohistochemistry, favoring Ewing and Ewing-like Sarcomas diagnosis (5A), and NKX2.2 negativity on immunohistochemical staining, ruling out Ewing sarcoma (5B).
Figure 6
Figure 6. Microscopic images showing S-100 negativity (A) and HMB-45 negativity (B) on immunohistochemical staining.
Figure 7
Figure 7. Microscopic images showing Desmin negativity on immunohistochemical stain, ruling out rhabdomyosarcoma (A), and PanCK negativity, ruling out synovial sarcoma (7B).
Figure 8
Figure 8. Microscopic images showing CD56 positivity on immunohistochemical stains, narrowing the differential to Ewing-like sarcomas, i.e., CIC-DUX4 and BCOR-CCNB3 sarcomas (A), and WT1 negativity, ruling out CIC-DUX4 Ewing-like sarcoma (B).
Figure 9
Figure 9. Microscopic images showing Cyclin D1 (A) and BCL2 (9B) positivity on immunohistochemical stain ruling in BCOR-CCNB3 sarcoma diagnosis.
See this image and copyright information in PMC

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