Intrasellar collision tumor of chordoma and pituitary adenoma: a rare case and literature review

Abstract Background Chordomas are rare intracranial neoplasms accounting for approximately 6% to 16% of all skull base lesions and 0.1% to 0.2% of all malignancies. First described by Ribbert in 1890, these tumors arise from undifferentiated notochordal remnants along the axial skeleton and exhibit a slow-growing but locally aggressive behavior. They most frequently occur in the sacrum, mobile spine, and clivus. Intrasellar chordomas are exceptionally rare and can closely mimic pituitary adenomas in terms of imaging and clinical presentation, potentially leading to misdiagnosis. Case report We present a 77-year-old female with a known pituitary macroadenoma previously treated with two transsphenoidal tumor excisions in 2007 (18 years ago) and in 2022 (3 years ago). She presented with acute left third cranial nerve palsy. MRI revealed an enlarging sellar mass, and she underwent a third endoscopic transsphenoidal tumor excision in 2025. Histopathological examination of the resected tumor revealed a chordoma. A retrospective review of previous surgical specimens (2022) confirmed the presence of both chordoma and pituitary adenoma, establishing the diagnosis of a collision tumor. Conclusion This case represents only the fifth documented instance of a collision tumor comprising both chordoma and pituitary adenoma in the sellar region. There is no standardized treatment protocol for sellar collision tumors involving chordoma and pituitary adenoma. Management should be guided by the chordoma component due to its aggressive biological behavior. A multidisciplinary approach and long-term surveillance are essential to optimize outcomes in these rare and complex cases.