case_images: PMC11828633_01
case_images: Clinical patient image showing unilateral proptosis in the left eye with epiphora (
  A
  ). Axial T1 postcontrast magnetic resonance imaging (MRI) showing an ill-defined lobulated lesion in the lateral aspect of the orbit in extraconal space displacing the globe anteriorly (
  B
  ). Coronal T1 postcontrast MRI showing the lesion abutting the superior and lateral rectus muscles with temporal bone invasion (
  C
  ).
case_images: 10-1055-s-0044-1792029-i2490003-1.jpg
case_images: PMC11828633_01_10-1055-s-0044-1792029-i2490003-1.jpg
case_images: FI2490003-1
case_images: PAX8, and K i -67 index of 15%. The patient underwent total thyroidectomy followed by high-dose RAI therapy. Post-RAI follow-up (8 months after RAI), he developed a sudden-onset swelling in the left orbital region ( Fig. 1A ). He was evaluated with MRI which revealed an ill-defined lobulated lesion in the lateral aspect of the orbit abutting the superior and lateral rectus muscles with temporal bone with invasion and no intracranial extension noted ( Fig. 1B and C ). 
case_images: [18F]-Fluorodeoxyglucose (FDG)-positron emission tomography-computed tomography (PET/CT), maximum intensity projection (MIP) image (
  A
  ) and sagittal fused image (
  B
  ) demonstrating hypermetabolic multiple lytic skeletal lesions at the calvarium, left orbit (red arrow), C2 vertebra, multiple ribs, L3 vertebra (blue arrow), multiple pelvic bone, and sacrum with intraspinal extension (blue arrow). Axial fused images (
  C
  ) showing [18F]FDG-avid (maximum standardized uptake value [SUVmax] 11.50) left lateral extraconal orbital metastasis (red arrow) and [18F]FDG-avid (SUVmax 14.50) L3 vertebral metastasis with compression fracture and associated soft tissue component (blue arrow).
  131
  I fused axial single-photon emission computed tomography (SPECT)/computed tomography (CT) images (
  D
  ) and whole-body MIP SPECT/CT image (
  E
  ) showing
  131
  I uptake in left lateral extraconal orbital metastasis, L3 vertebral lesion, and other skeletal lesions, but on comparison with [18F]FDG-PET/CT scan,
  131
  I scan showed lack of concentration in cervical and sacral metastatic lesions suggestive of dedifferentiation and aggressive disease.
case_images: 10-1055-s-0044-1792029-i2490003-2.jpg
case_images: PMC11828633_01_10-1055-s-0044-1792029-i2490003-2.jpg
case_images: FI2490003-2
case_images:  He underwent [18F]-fluorodeoxyglucose (FDG)-positron emission tomography-computed tomography (PET/CT), which showed increased uptake in left orbital lesion, multiple skeletal lesions, and lung lesions ( Fig. 2A-C ). Whole-body (WB) radioiodine ( 131 I) single-photon emission CT/ CT, showed radioiodine uptake in the metastatic left orbital lesion and multiple skeletal lesions ( Fig. 2D and E ).