A biopsy of a periapical lesion shows chronic inflammatory infiltrate, cholesterol clefts, and a lining of non-keratinized stratified squamous epithelium, associated with a tooth showing no response to cold testing. What is the most likely diagnosis?

A periapical (radicular) cyst is characterized radiographically by a well-defined periapical radiolucency associated with a non-vital (no response to cold) tooth, and histologically by a lining of non-keratinized stratified squamous epithelium with an underlying chronic inflammatory infiltrate, often including cholesterol clefts — distinguishing it from a periapical granuloma, which lacks any epithelial lining and consists of granulation tissue instead.