Biomechanical characterization of thyroid-stimulating hormone-secreting pituitary adenoma using in vivo MR elastography and in vitro nanoindentation: illustrative case.

backgroundThyroid-stimulating hormone (TSH)-secreting pituitary adenomas (TSHomas) are rare lesions that result in secondary hyperthyroidism. MR elastography (MRE) is an emerging imaging modality capable of assessing the mechanical properties of tissues, offering valuable insights into tumor consistency for improved preoperative planning and resection. OBSERVATIONS: A 16-year-old female diagnosed with a giant TSHoma underwent endoscopic transnasal transsphenoidal excision. The mechanical properties of TSHoma were assessed using preoperative MRE and in vitro nanoindentation on excised specimen. Collagen content was also evaluated. Based on its appearance on MRE, a neuroradiologist predicted the tumor would be soft, and it was found to be soft during the surgery. Interestingly, the in vitro shear storage and loss moduli closely match the in vivo findings. Additionally, the tumor tissue has up to 20% collagen content in intratumoral areas. LESSONS: MRE is a reliable and clinically valuable tool for preoperative evaluation of tumor consistency in rare TSHomas. The strong concordance between MRE findings, intraoperative texture, and in vitro mechanical measurements underscores the potential of MRE to guide surgical planning, reduce operative complexity, and improve clinical outcomes, especially in uncommon and challenging cases. https://thejns.org/doi/10.3171/CASE25402.