Capicua transcriptional repressor (CIC)-rearranged sarcoma represents a distinct pathologic entity and constitutes the second most prevalent category of undifferentiated round cell sarcomas (URCSs) after Ewing sarcoma. The 2 most common translocations are t(4;19) and t(10;19), resulting in CIC fusions with either DUX4 and DUX4L paralog, respectively; however, other rare variant fusions have also been reported. In this study, we expand the molecular spectrum of CIC-gene partners, reporting on 5 cases of URCSs showing CIC fusions with AXL, CITED1, SYK, and LEUTX by targeted RNA or DNA sequencing. There were 4 female patients and 1 male patient with a wide age range (12-70 years; median, 36 years). Four cases occurred in the deep soft tissues (lower extremity, 3; neck, 1) and 1 case in the central nervous system (midbrain/thalamus). All cases showed similar histologic findings within the spectrum of URCSs. Immunohistochemistry, showed variable positivity for ETV4 in 4 of the 4 cases and positive results for ERG in 3 of the 4 cases and for WT1 in 1 of the 4 cases. CD31 showed positivity in 2 of the 3 cases, including one coexpressing ERG. Unsupervised clustering of methylation profiles by T-distributed stochastic neighborhood embedding performed in 4 cases showed that all clustered tightly together and along the CIC sarcoma methylation class. RNA-sequencing data showed consistent upregulation of ETV1 and ETV4 mRNA in all cases examined, at similar levels to CIC::DUX4 URCSs. Our study expands the molecular diversity of CIC-rearranged URCSs to include novel and rare partners, providing morphologic, immunohistochemical, gene expression, and methylation evidence supporting their classification within the family of tumors harboring the more common DUX4/DUX4L partner genes.

CIC-rearranged sarcomas (CIC-RS) represent the most frequent subset of \"Ewing-like\" undifferentiated small round cell sarcomas. These tumors tend to be more aggressive than Ewing sarcomas. Moreover, treatment strategy can differ according to teams. The primary aim of this retrospective study was to describe the characteristics, treatments, and outcome for patients with CIC-RS included in the French NETSARC+ database.
Pediatric and adult patients from 13 French centers with a diagnosis of CIC-RS were registered from October 2008 to March 2021. Patients and tumors characteristics were collected from the national network NETSARC+ database (http://netsarc.sarcomabcb.org). CIC-RS diagnosis was pathologically and molecularly confirmed with a central review by expert pathologists. Two groups of patients were studied: those treated as classical Ewing sarcomas (cohort EwS) and those treated as high-grade soft tissue sarcomas (cohort STS) according to ESMO and/or EpSSG guidelines. Survival was calculated using the Kaplan-Meier method and the log-rank test was used to compare survival.
Among 79 patients, the male/female sex ratio was 0.7 and the median age at diagnosis was 27 years (range 2-87). With a median follow-up of 37 months, 39 patients died of the disease. Median overall survival from diagnosis was 18 months, with no significant difference between both cohorts (p = 0.9). Nevertheless, when focusing on patients with metastatic disease at diagnosis (N = 21), all patients from cohort STS died of disease while some patients from cohort EwS were still alive and in complete remission.
FSG experience confirms the aggressive clinical course of CDS patients regardless of chemotherapy regimen.

SMARCA4-deficient sarcoma was first reported in the chest and recently in the uterus, but not in the stomach. Here, we present a patient diagnosed with SMARCA4-deficient sarcoma of the stomach, using histochemistry. An emergency operation was performed due to perforation of the tumor. However, one month after the operation, two nodes recurred, and six cycles of combination chemotherapy consisting of adriamycin and ifosfamide were administered. The combination chemotherapy showed a remarkable effect, and complete remission was achieved. The patient was alive without recurrence after 48-month follow-up. SMARCA4-deficient sarcoma is an exceedingly rare tumor with an extremely poor therapeutic response to anticancer drugs. Herein, we present the first case of SMARCA4-deficient sarcoma of the stomach, where a complete response to chemotherapy was achieved.

BCOR-rearranged sarcoma is the third common subtype of undifferentiated small round cell sarcoma and was first recognized in 2012 from bone sarcoma with a similar morphological manifestation with undifferentiated round cell but totally different molecular hallmark from Ewing sarcoma. Primary BCOR-rearranged sarcomas were mostly found in bone and soft tissue and were sporadically reported in viscera involving kidney, which add difficulties in differential diagnosis. Here we present a 21 years old male patient with BCOR-CCNB3 in neck, which first diagnosed as thyroid cancer.

OBJECTIVE: To describe the pre-treatment imaging features and clinical course of undifferentiated round cell sarcomas with CIC-DUX4 and BCOR-CCNB3 translocations.
METHODS: In this retrospective study, several pre-treatment imaging features (tumor location, size, enhancement pattern, necrosis, flow voids, calcification, and FDG avidity) and the clinical course of patients were evaluated.
RESULTS: In 12 patients with CIC-DUX4 sarcomas (median age, 24 years; range, 12-75), sarcomas were located in the soft tissue (n = 10), bone (n = 1), and lungs (n = 1). On MRI, all 10 CIC-DUX4 sarcomas presented as a large necrotic mass (mean size 6.7 cm, range 2.3-11.3) with 100% demonstrating contrast enhancement, 60% showing flow voids, and 20% demonstrating fluid-fluid levels. On PET, the mean SUVmax was 13.2 (range, 8.5-18.1). Among 12 patients with follow-up, 3 died within a year of diagnosis. The most common site of metastases was the lungs (5/12). In 5 patients with BCOR-CCNB3 sarcomas (median age, 14 years; range, 2-17), sarcomas were located in the spine (n = 2), femur (n = 1), tibia (n = 1), and pelvis (n = 1). On radiograph or CT, 2 were lytic, 3 were sclerotic. Soft tissue calcifications occurred in 40% of BCOR-CCNB3 sarcomas. On MRI, all 3 BCOR-CCNB3 tumors enhanced with 33% demonstrating flow voids and 66% exhibiting necrosis. On PET, the mean SUVmax was 6.3 (range 5.7-6.9).
CONCLUSIONS: CIC-DUX4 sarcomas often present as necrotic and hypermetabolic soft tissue masses while sarcomas with BCOR-CCNB3 translocations are vascular bone lesions with necrosis at imaging. CIC-DUX4 sarcomas are clinically more aggressive than BCOR-CCNB3 sarcomas.

Certain genetically defined undifferentiated round cell sarcomas, namely BCOR-CCNB3 and CIC-DUX4 positive, have been described. Here we present detailed clinicopathologic features and molecular results in such cases.
Fifty one cases of undifferentiated round cell sarcomas, including 32 cases, tested for BCOR-CCNB3 and CIC-DUX4 fusions, by reverse transcription polymerase chain reaction technique and 44 tumours, for CCNB3 immunostaining, were analyzed.
Twenty seven (52.9%) tumours occurred in males and 24 (47%) in females; in soft tissues (38; 74.5%), commonly, trunk and extremities and bones (13; 25.4%), frequently, femur and tibia. Five of 32 (15.6%) tested cases were positive for BCOR-CCNB3 fusion and seven (21.8%) for CIC-DUX4 fusions. Histopathologically, CIC-DUX4-positive sarcomas comprised nodular aggregates of round to polygonal cells, containing hyperchromatic nuclei, prominent nucleoli and moderate cytoplasm, with focal myxoid stroma and variable necrosis, in certain cases. BCOR-CCNB3- positive sarcomas mostly comprised diffusely arranged, round to oval to short spindly cells with angulated nuclei, vesicular chromatin, inconspicuous nucleoli and interspersed vessels. Immunohistochemically, tumour cells were positive for MIC2 in 24 of 49 (48.9%) and CCNB3 in 12 of 44 (27.2%) cases. Four of five BCOR-CCNB3-positive sarcomas showed CCNB3 immunostaining and 6 of 7 CIC-DUX4-positive sarcomas displayed WT1 immunostaining. Most patients (27/37) (72.9%) underwent surgical resection and chemotherapy. Median overall survival was 12 months, and disease-free survival was seven months.
Undifferentiated round cell sarcomas are rare; mostly occur in soft tissues of extremities, with CIC-DUX4 positive, as these are relatively more frequent than BCOR-CCNB3 positive sarcomas. CCNB3 and WT1 are useful immunostains for triaging such cases for BCOR-CCNB3 and CIC-DUX4 fusion testing, respectively. Overall, these are relatively aggressive tumours, especially CIC-DUX4-positive sarcomas.

We experienced a case of primary malignancy in giant cell tumor of bone (GCTB), arising in the right femur and harboring H3F3A mutation. A 27-year-old Japanese male without any prior disease history complained of pain in his right hip joint and right lower limb. Radiological images revealed an osteolytic and multicystic lesion existing mainly at the proximal epiphysis of the right femur. Preoperative clinical diagnosis was GCTB, although irregular marginal sclerosis was an atypical radiographic finding for conventional GCTBs. Biopsy sample from the lesion revealed the coexistence of typical GCTB and undifferentiated high-grade round cell sarcoma. Despite of the wide local resection of the tumor with preoperative and postoperative chemotherapy, the patient died of multiple distant metastases of the tumor 9 months after the surgery. Since heterozygous H3F3A c. 103G>T (p. Gly34Trp) mutation was detected not only in the biopsy sample from the primary site with typical GCTB and high-grade sarcoma components but also in the resected material from the metastatic site with only pure high-grade sarcoma component, the tumor was considered originally derived from conventional GCTB and acquire malignant transformation to high-grade sarcoma. Thus, this is an extremely rare case of primary malignancy in GCTB and the first case report of primary malignancy in GCTB proved the presence of H3F3A mutation even in the sarcoma component.