ACTB::GLI1 Gene Fusion Small Bowel Mesenteric Tumor; a Case Report and Review of the Literature

Abstract

Abstract Introduction/Objective GLI1 encodes a transcription factor that targets cell cycle regulators affecting stem cell proliferation. Activation of the GLI (glioma-associated oncogene homologue 1). GLI activity in adult tissues is restricted but has been identified in various neoplasms, as a result of mutations in the PTCH (patched) or SMOH (smoothened) genes, encoding components of the sonic hedgehog pathway, or by amplification of GLI. The B-actin (ACTB) gene, encoding an essential cytoskeletal component, is under the control of a conserved, strong, and complex promoter that assures a high level of expression in non-muscle cells. ACTB::GLI1 gene fusions have been reported in the tongue as the pathognomonic genetic abnormality defining an unusual subset of actin-positive, perivascular tumors with t (7;12) translocation. Methods/Case Report We report a case of 53-year-old male presented to the hospital with dizziness and bloody stools. CT scan of the abdomen and pelvis revealed a 10.5 x 7.7 cm large complex cystic and solid mass of the right lower quadrant of the abdomen adjacent to the cecum and terminal ileum. The patient has a past medical history of testicular germ cell tumor and underwent orchiectomy with adjuvant chemotherapy 30 years ago. The mass was excised and histological examination of the mass showed an unencapsulated, relatively circumscribed neoplasm composed of sheets of monomorphic bland spindle to ovoid cells. Immunohistochemical (IHC) stains, including pan- CK, SALL4, c-Kit, CD34, SMA, MDM2, HMB45, and MART1, were all negative. NGS sarcoma fusion panel was done and revealed ACTB::GLI1 gene fusion. The tumor was finally diagnosed as GLI1 -rearranged enteric tumor. Results (if a Case Study enter NA) NA Conclusion our case, in addition to, previously reported cases in the literature support the existence of a newly identified, seemingly discrete group of soft tissue tumors at different body locations. The morphology of these tumors is somewhat variable, making identifying and diagnosing these tumors more challenging. In addition to the morphologic variance, the diagnosis of these tumors in unusual locations is not uncommon, with some variations in IHC staining patterns. Identifying the molecular pattern of these tumors and the biological mechanism will facilitate more effective treatment options for patients, including targeted therapy.