An unusual association of deletion of SMARCB1 in a patient with intracranial yolk sac tumor: A case-report

Background: Deletion of SMARCB1/loss of INI is a well-known association in atypical rhabdoid teratoid tumors (ATRT) in the brain, rhabdoid tumors in the kidney, and less common tumors, including sinonasal INI1 deficient carcinoma, gastric undifferentiated carcinoma, undifferentiated uterine sarcomas, and poorly differentiated chordomas. Case report: We describe homozygous deletion of the SMARCB1 gene in a patient diagnosed with pineal yolk sac tumor, which is a rare entity. The association highlights the importance of INI1 staining when the clinical course is not progressing as expected and raises a critical management question: should this rare entity be treated aggressively, like ATRT, versus the conventional approach to intracranial yolk sac tumor? Conclusion: This case highlights the importance of INI1 staining in pediatric primitive central nervous system tumors as some germ cell markers are expressed in rhabdoid tumors at the stem cell level, implicating the germ cell origin of ATRT, which can complicate the diagnosis.