Q. A 59-year-old man with a longstanding history of gastroesophageal reflux disease (GERD) attends a routine check-up. He has been on proton pump inhibitor therapy for 10 years, managing his symptoms effectively. He has been a smoker since the age of 22. Considering his medical history and risk factors, you recommend an upper endoscopy and biopsy to evaluate Barrett's esophagus. Which of the following histological changes are characteristic of Barrett's esophagus?