We evaluated BRG1 and INI1 expression in 12 SCCOHTs and in a series of 122 tumors that could mimic SCCOHT morphologically: 9 juvenile granulosa cell tumors, 47 adult granulosa cell tumors, 33 high-grade ovarian serous carcinomas, 9 desmoplastic round cell tumors, 13 Ewing sarcomas (5 from the pelvis and 8 from soft tissues), 1 round cell sarcoma associated with CIC-DUX4 translocation from soft tissue (thigh), 1 case of high-grade endometrial stromal sarcoma of the ovary, and 9 melanomas.
By RT-PCR, fusion transcripts involving CIC (19q13) and DUX4 (4q35) were confirmed to be present in both primitive round cell sarcomas, further defining the breakpoints seen by genomic analysis.
As such the WHO classification temporarily grouped the CIC-rearranged tumors under undifferentiated sarcomas with round cell phenotype, until further clinical evidence was available.
In this review we discuss the main categories of undifferentiated round cell sarcoma, in relation to Ewing sarcoma and its molecular variants, with particular emphasis on the genetic and biologic features of recently described entities including desmoplastic small round cell tumor and CIC-DUX4 as well as BCOR-CCNB3-associated round cell sarcomas.
In conclusion, NKX2.2, ETV4 and BCOR IHC may be helpful in daily practice for distinguishing ESFT from CIC or BCOR-associated sarcomas, especially in hospitals without access to molecular assays.
These findings are cautionary regarding use of these immunostains in prospective case workup, whereas the prevalent MYC amplification may represent a therapeutically targetable oncogenic pathway in CIC-DUX sarcomas.
ETV transcriptional upregulation is more reliable than RNA sequencing algorithms and FISH in diagnosing round cell sarcomas with CIC gene rearrangements.
In light of morphologic features that overlap with those of NC from typical anatomical sites we have seen previously, the tumor was best classified as falling within the NC spectrum rather than CIC-associated sarcoma.
A histologic comparison of the CIC-rearranged sarcomas with 20 EWSR1-rearranged Ewing sarcomas showed significantly higher degrees of lobulation, nuclear pleomorphism, the prominence of the nucleoli, spindle cell elements, and myxoid changes in the CIC-rearranged sarcomas.
The spectrum of ELS is now expanding, and additional gene fusion partners besides DUX4 or CCNB3 have been detected, and the terms CIC or BCOR-rearranged sarcomas have recently been proposed.
This case report describes an additional case of <i>CIC-DUX4</i> sarcoma with a novel fusion breakpoint, and demonstrates the value of this next-generation sequencing-based anchored multiplex PCR technique (Archer FusionPlex Sarcoma Panel) in both diagnosis for patient care and in identification of a novel fusion breakpoint in this tumour type.