Figure 1 52-year-old male. (a) Panoramic and (b) occlusal radiographs, left: panoramic and occlusal radiographs of primary lesion shows multilocular radiolucency with well-defined margin on the right mandibular body. (a, centre) Panoramic radiography after surgery shows that the surgical defect of the mandible was primarily reconstructed with a free iliac crest bone graft. (a) Panoramic and (b) occlusal radiographs, right: panoramic and occlusal radiographs of recurrent lesion shows a large multilocular radiolucency occupying the whole graft bone with a relatively well-defined border. (c) Computed tomography (CT) of recurrent lesion shows expansion of the tumour mass to adjacent soft tissue at the buccal side on soft tissue shadow imaging and expansion, thinning and perforation of cortical outline of graft bone with multilocular radiolucency. Left; soft-tissue target condition, right; bone target condition. (d) MRI of recurrent lesion shows homogeneous intermediate signal intensity (SI) on T₁ weighted imaging (T1WI), heterogeneous high SI with more high SI area on T₂ weighted imaging (T2WI) (left) and disproportionate signal enhancement with no enhanced spot on contrast enhanced (CE)-T1WI (right). (e) Histopathology of primary lesion (upper, haematoxylin and eosin (HE) stainx100) revealed extensive squamous metaplasia associated with keratin formation in the central portions of the epithelial islands of a follicular ameloblastoma. Therefore, the lesion was diagnosed as an acanthomatous ameloblastoma with a follicular pattern. Histopathology of the recurrent lesion (lower, HE stainx100) shows a combination of follicular and plexiform microscopic patterns with cystic degeneration at both the central portion of the follicle pattern and the stroma of the plexiform pattern