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(A and B) MRI axial T1-weighted images show a multilobulated expansile mass with (A) intramedullary and (B) subperiosteal components. Most of the lobulations exhibit concentric ring signs which signify chronic haematomas. The concentric ring sign consists of a hypointense outer rim (white arrow) and hyperintense inner rim (black arrow). The core of the lesion shows heterogeneous intermediate signal intensity reflecting different stages of blood degradation products (asterisk).
