Capicua transcriptional repressor (CIC)-rearranged sarcoma harboring CIC-LEUTX fusion with renal involvement: a rare case report.

Background: Capicua transcriptional repressor (CIC)-rearranged sarcoma (CRS) is a rare and highly aggressive undifferentiated small round cell sarcoma (USRCS), which genetically displays a characteristic gene fusion between CIC gene with other genes such as DUX4.

Case description: We report a rare case with CIC-LEUTX fusion. The 45-year-old male patient presented to our department with frequent dry cough and lumbar pain. Computed tomography (CT) scan indicated multiple pulmonary nodules on both sides, hilar lymph node enlargement, left lower lobe infection and presence of pleural effusion in left quadrant. Enlargement and uneven density were seen in the left kidney, together with perinephric exudate, renal calculi, thickening and filling deficiency in renal veins, and small retroperitoneal lymph nodes. Immunohistochemistry (IHC) showed negativity in CK7, CK20, CD10, vimentin, PAX-8, P63, MelanA and synapatophysin, but GATA3 and CK were positive. RNA-based next generation sequencing (NGS) detection revealed CRS of gene fusion in CIC (exon 20) and LEUTX (exon 3). After treatment with a variety of targeted and chemotherapy drugs, the patient showed a poor response with a survival time of merely 7 months.

Conclusions: This case of USRCS harboring CIC-LEUTX fusion with renal involvement could help to expand our understanding on the diagnosis and treatment of CRS harboring CIC-LEUTX fusion.