On a plain radiograph (X-ray) I reviewed recently, I encountered a classic lesion straight out of a textbook: A broad-based bony outgrowth located at the proximal medial metaphysis of the tibia, demonstrating clear corticomedullary continuity with the parent bone and projecting distally (downward) away from the growth plate. When we first encounter this image, a single term immediately comes to mind: Exostosis. However, right at this juncture, one of the most intriguing debat

Keywords: Thin capsule , subcutaneous location 🔹 Clinical: Slowly growing, subcutaneous lesion Located close to the skin surface Stable for more than 2 years 🔹 CT findings (non-contrast, 2 years ago): Central cystic appearance Surrounding dirty fat planes → chronic inflammatory reaction Stability over time favors a benign process 🔹 MRI findings (current): T1: Hypointense T2: Mildly hyperintense (not as bright as pure fluid, due to keratin/debris) Capsule: Thin, well-define