BCOR-CCNB3 rearranged sarcoma arising in neck misdiagnosed as thyroid cancer: A case report

Clinical Characteristics of Children with Nasal BCOR-Rearranged Ewing-like Sarcoma: A Case Report and Literature Review

Ewing-like sarcomas (ELS) are round cell mesenchymal neoplasms that are highly aggressive to bone and/or soft tissue. However, they rarely occur in the nose, with no reported such cases in the medical literature to date. Here, we reported the case of a two-year-old Chinese boy who presented with a mass in the left nasal cavity. Surprisingly, the final histopathological diagnosis of the nasal mass was determined to be a subtype of ELS, BCOR-rearranged sarcoma. Therefore, we retrospectively analyzed the clinical data of this case and reviewed the relevant literature on ELS and BCOR-rearranged sarcoma. The purpose of this article is to provide new insights into the clinical characteristics of children with BCOR-rearranged Ewing-like sarcoma and to improve the understanding of this disease.

The utility of FISH analysis in the diagnosis of BCOR-rearranged sarcomas

BACKGROUND

A BCL6 corepressor (BCOR) gene alteration is a genetic signature of rare subsets of sarcomas. The identification of this alteration has recently contributed to the definition of new entities in the current WHO (2020) classification of soft tissue and bone tumours. We retrospectively examined cases of BCOR-rearranged sarcoma (BRS) to assess the reliability of the BCOR FISH analysis using an IVD (in vitro diagnostic) probe.

METHODS

We investigated and compared the molecular diagnostic strategies and features by collecting 17 data from patients with a BCOR gene rearrangement detected using quantitative-Reverse Transcription-Polymerase Chain Reaction (qRTPCR), Next-Generation Sequencing (NGS) and Fluorescence in situ hybridization (FISH).

RESULTS

We describe fourteen BCOR::CCNB3 sarcomas, one spindle cell sarcoma with a novel BCOR::MAML1 fusion, one spindle cell sarcoma with a novel BCOR::AHR fusion, and one ossifying fibromyxoid tumour with a BCOR::ZC3H7B fusion. FISH analysis of all, except one, BCOR::CCNB3 sarcoma, showed a FISH break-apart pattern with mild signal separation. The MAML1::BCOR sarcoma showed large-space split signals, while in the two patients with AHR::BCOR and ZC3H7B::BCOR fusions, no BCOR rearrangement was observed using FISH.

CONCLUSIONS

Our study indicates that BCOR FISH analysis using an IVD probe, may be useful to detect the presence of a BCOR rearrangement, including both translocations and inversions; however, negative results, in some cases, can occur.

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

Sarcoma with BCOR genetic alteration is an exceptionally rare and emerging subtype of sarcoma. It is categorized into two types: BCOR-related gene fusions such as BCOR::CCNB3 sarcomas and other BCOR-rearranged sarcoma and sarcomas with internal tandem duplication of BCOR genes such as infantile undifferentiated round cell sarcomas and primitive myxoid mesenchymal tumors of infancy. BCOR::CCNB3 sarcomas predominantly arise in bone rather than soft tissue and exhibit a higher occurrence in children and adolescent males, whereas sarcomas with BCOR internal tandem duplication show a wider age range but usually arise in the first year of life. Due to their rarity, there is ongoing debate and uncertainty regarding the best treatment approach, with a lack of specific clinical trials addressing these tumors. In this report, we present a unique case of sarcoma with internal tandem duplication of BCOR gene originating in the nasal region. The tumor was successfully and completely resected using the standard VDC-IE chemotherapy protocol, resulting in an unprecedented 100 percent tumor necrosis. The patient has completed the protocol and remains recurrence-free 13 months after diagnosis. This case suggests potential efficacy of the standard VDC-IE protocol in achieving remarkable responses in BCOR rearrangement sarcomas, including the internal tandem duplication subtype. However, further studies are needed to determine the optimal treatment strategies for this disease.

Small round cell sarcomas

Undifferentiated small round cell sarcomas (SRCSs) of bone and soft tissue comprise a heterogeneous group of highly aggressive tumours associated with a poor prognosis, especially in metastatic disease. SRCS entities mainly occur in the third decade of life and can exhibit striking disparities regarding preferentially affected sex and tumour localization. SRCSs comprise new entities defined by specific genetic abnormalities, namely EWSR1-non-ETS fusions, CIC-rearrangements or BCOR genetic alterations, as well as EWSR1-ETS fusions in the prototypic SRCS Ewing sarcoma. These gene fusions mainly encode aberrant oncogenic transcription factors that massively rewire the transcriptome and epigenome of the as yet unknown cell or cells of origin. Additional mutations or copy number variants are rare at diagnosis and, depending on the tumour entity, may involve TP53, CDKN2A and others. Histologically, these lesions consist of small round cells expressing variable levels of CD99 and specific marker proteins, including cyclin B3, ETV4, WT1, NKX3-1 and aggrecan, depending on the entity. Besides locoregional treatment that should follow standard protocols for sarcoma management, (neo)adjuvant treatment is as yet ill-defined but generally follows that of Ewing sarcoma and is associated with adverse effects that might compromise quality of life. Emerging studies on the molecular mechanisms of SRCSs and the development of genetically engineered animal models hold promise for improvements in early detection, disease monitoring, treatment-related toxicity, overall survival and quality of life.

Soft Tissue and Visceral Organ Sarcomas With BCOR Alterations

Sarcomas with BCOR alteration are a heterogenous group characterized by changes including internal tandem duplications (ITDs) and recurring fusions with CCNB3, ZC3H7B, and other rare partners. With widespread genomic testing, these alterations are now associated with histologies such as Ewing-like sarcoma (BCOR::CCNB3), high-grade endometrial stromal sarcoma (ZC3H7B::BCOR), and clear cell sarcoma of kidney (BCOR-ITD). BCOR altered sarcomas of soft tissues and organs were identified through PubMed using keywords "Sarcoma (AND) BCOR" from 2005 through October 2021. Summary statistics and outcome data were calculated using STATA v12.1. Forty-one publications described 190 patients with BCOR altered soft tissue or organ sarcomas. BCOR-ITD was most common, followed by BCOR::CCNB3, ZC3H7B::BCOR. BCOR-ITD tumors occurred mainly in infants, BCOR::CCNB3 commonly occurred in adolescent young adults, and ZC3H7B::BCOR only in adults. The most common site for BCOR::CCNB3 fused tumors was extremity, BCOR-ITD kidney and ZC3H7B::BCOR uterus. Metastasis was rare in patients with BCOR::CCNB3. While most underwent resection and chemotherapy, few received radiation. Median follow-up of survivors was 24 months. Five year overall survival for patients with BCOR::CCNB3 fusions was 68% (95% confidence interval [CI]: 46%-83%). Patients with BCOR-ITD and ZC3H7B::BCOR had worse prognoses with 5 years overall survival of 35% (95% CI: 15%-56%) and 41% (95% CI: 11%-71%), respectively, demonstrating need for collaborative efforts identifying optimal treatments to improve outcomes.