Gardner syndrome

A 29-year-old woman with a strong family history of colorectal cancer attends the clinic for a screening colonoscopy. The colonoscopy results, shown below, are suspicious for an inherited condition caused by a mutation in chromosome 5. On systemic examination, the patient has widespread epidermoid cysts, particularly noticeable on the face and extremities, and an abnormal growth in her mandible. Considering the clinical presentation, which of the following is the most likely diagnosis?