A Rare Case with KMT2D: BCOR Fusion Alteration Sarcoma in A 14-Year-Old-Female

Abstract Introduction/Objective Tumors with BCL6-correpresor gene (BCOR) alteration are a heterogeneous group of undifferentiated sarcomas, occurring in various age groups and anatomic sites, characterized by spindle and round cell phenotype and diffuse immunoreactivity for BCOR. With widespread genomic testing, these alterations are now associated with different histologies. These sarcomas show a striking male predominance and occur in children/ adolescents. Methods/Case Report The Patient was a 14 years-old female presented after an accident with RLQ abdominal pain. Her pan-CT showed a 9.0 x 5.5 x 4.0 cm omental mass with free pelvic fluid in the anterior and upper pelvis. Results (if a Case Study enter NA) Microscopic examination showed lobulated spindle cell tumor with myxoid areas, extensive necrosis, focal calcifications, and perivascular lymphocytic infiltrates The tumor composed of bundles of monotonous cells with bizarre nuclei. Mitoses were brisk (44 mitoses per 10HPF). The tumor appeared to infiltrate adipose tissue and it had peritheliomatous pattern of proliferation. Beta-catenin, inhibin, BCL2, and Pan-TRK were positive in the spindle cells. PAX8 showed patchy positivity. EMA, CAM5.2, DOG-1, CD117, ALK1, CD34, HMB45, STAT6, SMA, CD31, S100, CD99, p63, SALL-4, CD10 were negative. Trichrome highlighted the intervening fibrous septae. Molecular Next Generation Sequencing studies showed a structural genomic alteration between the KMT2D and BCOR genes [t(12;X)(12q13.11;Xp11.4)]. Conclusion Tumors harboring rare fusion variants of BCOR, such as BCOR- KMT2D, were also positive for pan-TRK staining and NTRK3 overexpression. These rearrangements are so rare. And therefore, efficient diagnosis of BCOR rearranged sarcomas can be achieved by using a combination of FISH and RT-PCR assays. The therapeutic implication of this finding awaits further investigation.