Fig. 1. CT images of chondroblastoma with secondary aneurysmal bone cyst in the sphenoid sinus in a 13-year-old boy.A. On pre-contrast axial plane image, a localized multilobulated, multiseptated small cystic mass (about 35 × 40 × 40 mm in size) involving the both sphenoid sinuses, posterior ethmoid sinuses, both frontal bases, right optic foramen, and right anterior cavernous sinus area is observed. High-attenuation lesion suggesting hemorrhage (arrow, about 40 HU) is observed inside the mass. A few foci of calcification (arrowhead, about 140 HU) are identified both inside the lesion and on the periphery of the lesion. B. The mass shows heterogeneous enhancement on post-contrast CT image. Note that the lateral border of the tumor (arrowheads) is well delineated; however, the anterior border (arrow) is ambiguous on CT. C. On post-contrast enhanced coronal plane image, the mass involves the sphenoid sinus and sellar floor. Extension into the right optic foramen (arrow) is suspected, but not obvious. D. On a bone window setting, bony erosion of the ethmoid roof and sellar floor is well visualized. HU = Hounsfield unit Fig. 1. CT images of chondroblastoma with secondary aneurysmal bone cyst in the sphenoid sinus in a 13-year-old boy.A. On pre-contrast axial plane image, a localized multilobulated, multiseptated small cystic mass (about 35 × 40 × 40 mm in size) involving the both sphenoid sinuses, posterior ethmoid sinuses, both frontal bases, right optic foramen, and right anterior cavernous sinus. . . J Korean Soc Radiol. 2017 Jan;76(1):61-66. https://doi.org/10.3348/jksr.2017.76.1.61