Hole within a hole sign

The hole within a hole sign or bevelled edge sign describes one classic appearance of lytic skull lesions in patients with eosinophilic granuloma. The bevelled edge of the defects indicates asymmetrical destruction of both inner and outer tables of the skull, giving the appearance of two overlapping lytic lesions of unequal size on x-ray .

The other common appearance for a lytic lesion of eosinophilic granuloma is a "punched out" lesion with well-defined margins and a non-sclerotic border .