CIC-rearranged sarcomas (CRS) are a group of heterogeneous tumors which mostly occur in the soft tissues of limbs and trunk, and are highly invasive with poor prognosis. Here, we describe a rare case of CRS that occurred in the left kidney with a CIC-LEUTX rearrangement.
A 45-year-old male was admitted to hospital with a dry cough for more than two months without obvious cause. Physical examination and laboratory tests revealed no notable abnormality. The CT scan demonstrated a mass in the left kidney and multiple nodules in both lungs. The percutaneous core needle biopsy showed similar histomorphology and immunophenotype of small round cell malignant tumors. Genetic test revealed a CIC-LEUTX gene fusion.
We present a rare primary renal CRS with multiple pulmonary metastases, and LEUTX is confirmed as the fusion partner of CIC gene for the first time in a renal case.

CIC-rearranged sarcoma is a rare and extremely aggressive tumor that occurs mainly in soft tissues. Despite the fact that identification of a characteristic genetic rearrangement is necessary to verify the diagnosis, in most cases, the correct diagnosis can be made by comparing histological signs and a characteristic immunophenotype, which greatly speeds up the diagnosis. The article describes a case of CIC-rearranged sarcoma in a 14-year girl with the successful application of the CWS-2009 treatment protocol.
CIC-перестроенная саркома является редкой и крайне агрессивной опухолью, которая возникает преимущественно в мягких тканях. Несмотря на то что для верификации диагноза необходима идентификация характерной генетической перестройки, в большинстве случаев верный диагноз может быть поставлен при сопоставлении гистологических признаков и характерного иммунофенотипа, что значительно ускоряет диагностику. В статье описано наблюдение CIC-перестроенной саркомы у 14-летней девочки с успешным применением протокола лечения CWS-2009.

According to the recent World Health Organization (WHO) classification, CIC-rearranged sarcomas, including CIC::DUX4-positive sarcomas constitute an aggressive subtype of undifferentiated round cell sarcomas. There is a single study on these tumors from our subcontinent. We present clinicopathological features of 5 additional cases of this tumor entity, including literature review. Thirty-nine undifferentiated round cell sarcomas, excluding Ewing sarcomas (ES), were tested for CIC::DUX4 fusion, including Type I (165 base pair size) and II (230 bp) by reverse transcription-polymerase chain reaction. Twenty-five of those tumors were tested for EWSR1 gene rearrangement, 5 for SS18 and 4 for SS18::SSX fusion, and were negative for those tests. Five tumors (12.8 %) were positive for CIC::DUX4(Type II) fusion. Five CIC:: DUX4-positive sarcomas occurred in 4 males and one female; of 25-43 years of age, in soft tissues, including thigh (n = 2), chest wall (n = 1), iliac region (n = 1) and foot (n = 1). Tumor size varied from 2.2 to 19 cm. Microscopically, the tumors were predominantly composed of nodules and sheets of malignant round to epithelioid cells, including \"rhabdoid-like\" (n = 2) and spindle-shaped (n = 2) with eosinophilic to vacuolated cytoplasm (4/5), distinct nucleoli (4/5), brisk mitoses, focal myxoid to hyalinised stroma (4/5) and necrosis (5/5). Immunohistochemically, tumor cells were positive for WT1 (5/5), calretinin (3/4), pan-keratin (1/4), CD99/MIC2 (\"dot-like\" to cytoplasmic membranous) (4/4), while negative for desmin (0/4), S100P (0/4), and NKX2.2 (0/5). INI1/SMARCB1 was retained (3/3). All patients underwent excision with adjuvant radiotherapy and chemotherapy (Ewing sarcoma regimen). A single patient developed recurrence, and 2 developed pulmonary metastasis, including one with brain metastasis. CIC:: DUX4-positive sarcomas are ultra-rare tumors, that mainly occur in the soft tissues and in young adult patients. Histopathologically, these tumors display a wide spectrum, including round to epithelioid cells, variable amount of cytoplasmic vacuolization and myxoid stroma with necrosis. Immunohistochemically, these tumors express WT1 and calretinin. Despite adjuvant therapies, these tumors have dismal outcomes, especially in large-sized tumors. CIC::DUX4-positive sarcomas need to be differentiated from their histopathological mimics, including ES, in view of significant treatment-related implications.

Primary bone tumours can pose diagnostic problems due to their overlapping radiologic and histologic features. Given the recent advancement in our understanding of the biology of bone tumours, multiple immunohistochemical and molecular markers have been devised to aid in their diagnosis. This review provides brief updates on select bone tumours, including chondrosarcomas, benign chondrogenic tumours, osteosarcomas, benign osteogenic tumours, fibroosseous lesions, vascular tumours, osteoclastic giant cell-rich or cystic tumours, chordoma, adamantinoma, small round blue cell sarcomas, and others. We discuss their salient molecular features and novel immunohistochemical correlates, along with some tips to avoid common diagnostic pitfalls.

CIC-rearranged sarcoma is a recently established, ultra-rare, molecularly defined sarcoma subtype. We aimed to further characterise clinical features of CIC-rearranged sarcomas and explore clinical management including systemic treatments and outcomes.
A multi-centre retrospective cohort study of patients diagnosed between 2014-2019.
Eighteen patients were identified. The median age was 27 years (range 13-56), 10 patients were male (56%), 11 patients (61%) had localised disease and 7 patients had advanced (metastatic or unresectable) disease at diagnosis. Of 11 patients with localised disease at diagnosis, median overall survival (OS) was 40.6 months and the 1-, 2- and 5-year OS estimates were 82%, 64% and 34% respectively. Nine patients (82%) underwent surgery (all had R0 resections), 8 (73%) patients received radiotherapy to the primary site (median dose 57Gy in 28 fractions), and 8 (73%) patients received chemotherapy (predominantly Ewing-based regimens). Metastases developed in 55% with a median time to recurrence of 10.5 months. In patients with advanced disease at diagnosis, median OS was 12.6 months (95% CI 5.1-20.1), 1-year OS was 57%. Median progression-free survival was 5.8 months (95% CI 4.5-7.2). Durable systemic therapy responses occurred infrequently with a median duration of systemic treatment response of 2.1 months. One durable complete response of metastatic disease to VDC/IE chemotherapy was seen. Responses to pazopanib (n = 1) and pembrolizumab (n = 1) were not seen.
In this series, CIC-rearranged sarcomas affected young adults and had a high incidence of presenting with, or developing, metastatic disease. The prognosis overall was poor. In advanced disease, durable systemic therapy responses were infrequent.

BACKGROUND Undifferentiated small blue round cell sarcomas with CIC-DUX4 translocation differ morphologically and in clinical outcomes from other types of sarcoma. Although classified by the World Health Organization as undifferentiated sarcomas, it is unclear whether these tumors are variants of Ewing\'s sarcoma or a distinct entity. This report describes a round cell sarcoma with CIC-DUX4 translocation that presented clinically as a phlegmon. CASE REPORT A 31-year-old African American man presented with a mass in the right upper abdominal quadrant. Examination at a local hospital suggested an intra-abdominal abscess, and incision and drainage were performed. One week later, he returned with increased pain and bloody drainage from the incision site. Computed tomography showed a complex solid-cystic area measuring 7.8 cm suggesting a large phlegmon/abscess or neoplasm. Histologically, the sarcomatous malignancy was cellular, multinodular, and necrotic, with cells having round-ovoid to spindled nuclei and variable amounts of pale cytoplasm. Immunohistochemically, the mass was focally positive for CD99, but much less positive than an Ewing sarcoma. The mass also showed diffuse nuclear positivity for WT-1 and ETV4, but was negative for desmin. Fluorescence in-situ hybridization showed positivity for CIC-DUX4 gene fusion, resulting in a final diagnosis of round cell sarcoma with CIC-DUX4 translocation. The patient has completed 14 cycles of chemotherapy with no evidence of metastasis or local recurrence. CONCLUSIONS A round cell sarcoma with CIC-DUX4 translocation can present clinically as a phlegmon with pleomorphic morphology. Early tumor identification by molecular analysis and early initiation of treatment can improve patient prognosis.

BACKGROUND: Despite extensive immunohistochemical (IHC) and molecular studies combined with morphologic findings, a group of round/ovoid cell tumors histologically similar to Ewing sarcomas (ES) but lacking EWSR1-rearrangements may remain unclassifiable.
METHODS: We retrospectively analyzed 41 Ewing-like tumors (formalin-fixed, paraffin-embedded) previously determined as negative or non-informative for EWSR1-rearrangements by FISH and/or RT-PCR. A new histopathology revision and additional IHC and molecular analyses were carried out in order to investigate whether additional IHC and/or molecular testing in combination with the morphological findings may help in reaching a definitive diagnosis.
RESULTS: Almost all the tumors (n=40) involved soft tissue and/or bone and half the patients died of disease. In the archival cases all diagnoses were Ewing sarcoma (ES), Ewing-like sarcoma (ELS), myoepithelial tumor and undifferentiated sarcoma (US). In the new review all the tumors were re-classified as, ES (n=16), Ewing-like tumor with EWSR1 rearrangement and amplification and possible EWSR1-NFATC2 gene fusion (n=1), CIC-rearranged sarcomas or undifferentiated sarcoma, most consistent with CIC-rearranged sarcoma (n=7), sarcoma with BCOR-alteration or undifferentiated sarcoma, consistent with BCOR-associated sarcoma (n=3), neuroblastoma (n=2), unclassifiable neoplasm with neuroblastic differentiation (n=1), malignant rhabdoid tumor (n=2), lymphoblastic lymphoma (n=1), clear cell sarcoma of the gastrointestinal tract (n=1), small cell carcinoma (n=1), sclerosing rhabdomyosarcoma (n=1), desmoplastic small round cell tumor (n=1), malignant peripheral sheath nerve tumor (n=1), poorly-differentiated synovial sarcoma (n=1), Possible gastrointestinal stromal tumor/GIST with predominant round cells (n=1) and possible SMARCA4-deficient-sarcoma (n=1). NKX2.2, ETV4 and BCOR immunoreactivity was observed in all ES, CIC-rearranged sarcomas and sarcomas with BCOR alteration, respectively. CIC-rearrangement by FISH was observed in many of the CIC-rearranged sarcomas.
CONCLUSIONS: Our analysis of 41 Ewing-like tumors confirms that there may be a significant pathological and IHC overlap among Ewing-like tumors, with prognostic and therapeutic impacts. Additional IHC (NKX2.2, ETV4 and BCOR) and molecular studies including FUS, CIC or BCOR analysis may support the final diagnosis when FISH or RT-PCR fail to detect EWSR1-rearrangements. Any molecular findings should always be interpreted in relation to the specific clinical and pathological context.

The literature is reviewed regarding of a rare molecularly defined group of sarcomas with rearrangement of both CIC and BCOR genes, which were originally placed into the EWSR1wt Ewing-like category. Personal experience with three cases demonstrating difficulties of this issue is added. Both groups of lesions differ not only by age and topography, but also vary in both the prognostic and the predictive parameters. CIC-rearranged tumors are very aggressive and almost never occur in the skeleton; in contrary, the BCOR-rearranged ones are predominantly bone tumors in young males behaving even better than classical Ewing sarcoma. From the morphologic point of view, it turned out to be a salient finding that these types of neoplasm might leave canonical morphotype of small blue round cell sarcoma. Instead of it, they are not uncommonly characterized as a relatively uniform spindle cell proliferation with prevailing myxoid transformation deserving much broader differential diagnosis. Our three cases reports display difficulties in reaching the correct diagnosis even by implementing sophisticated molecular techniques in routine practice. Notwithstanding of exhaustive molecular assays used, one may still encounter a lesion where original descriptive term Ewing-lie sarcoma remains uncorrected.

BACKGROUND: A subset of undifferentiated small round cell sarcomas (USRCSs) is currently being recognized as emerging entities with unique gene fusions: CIC-DUX4 (the area of focus in this article), BCOR-CCNB3, or CIC-FOXO4 gene fusions. CIC-DUX4 and CIC-FOXO4 fusions have been reported in soft tissue tumors, while BCOR-CCNB3 fusion with an X chromosomal inversion was described in both bone and soft tissue tumors. CIC-DUX4 fusion can either harbor t(4;19)(q35;q13.1) or t(10;19)(q26.3;q13), while t(4;19)(q35;q13.1) is reported more commonly.
METHODS: The aim of this study is to share a new case report of a 36-year-old woman who had a rapidly growing mass in her right upper thigh, which was found to be an undifferentiated small round cell sarcoma with t(4;19)(q35;q13.1) CIC-DUX4 fusion was confirmed by cytogenetic testing. Combined modality treatment with surgery, radiation, and chemotherapy was used and achieved a good response. A review of the literature of the reported cases with CIC-DUX4 fusions including both t(4;19) and t(10;19) translocations revealed a total of 44 cases reported. Out of these 44 cases, 33 showed t(4;19)(q35;q13.1) translocation compared to 11 cases with t(10;19)(q26.3;q13).
CONCLUSIONS: Undifferentiated small round cell sarcomas are aggressive tumors. Their treatment includes surgery, chemotherapy, and radiation. Resistance to chemotherapy is common. Lung and brain are common sites of metastasis, with associated poor prognosis. Generally, median survival is less than 2 years. Newer techniques have been developed recently which helped identify a subset of previously unclassifiable sarcomas, with promising prognostic value.

Desmoplastic small round cell tumour (DSRCT) is a rare tumour, usually arising in the abdominal cavity. DSRCT remains an aggressive malignancy, with a poor prognosis despite multi-modality treatments. In the published literature, there has been no patient who lived for three years or more without surgical excision. This report describes a case of DSRCT arising from the brachial plexus and successfully treated with caffeine-assisted chemotherapy. A 29-year-old male presented with pain and numbness in his left forearm. Radiological findings were suggestive of malignant tumour. Histology, immunohistochemical stain and fluorescence in situ hybridisation (FISH) results confirmed the diagnosis of DSRCT. He underwent caffeine-potentiated chemotherapy and the tumour disappeared. The tumour was not removed surgically as it was intertwined in the brachial plexus. Four years after the initial diagnosis, no local relapse and no distant metastases have been observed. Therefore, it is concluded that caffeine-assisted chemotherapy should be one of the treatment options for DSRCT.