**Core Concept**
The patient's symptoms suggest gastroesophageal reflux disease (GERD), characterized by the reflux of gastric contents into the esophagus, leading to inflammation and potential complications. This condition is often associated with anatomical and functional abnormalities of the lower esophageal sphincter (LES).

**Why the Correct Answer is Right**
The patient's symptoms of substernal chest pain, exacerbated by large meals, cigarettes, and caffeine, and relieved by antacids, are classic for GERD. The LES is normally a high-pressure zone that separates the esophagus from the stomach, but in GERD, it becomes incompetent, allowing gastric reflux into the esophagus. This chronic exposure to acidic gastric contents can lead to columnar metaplasia of the distal esophagus, also known as Barrett's esophagus. This condition is a precursor to esophageal adenocarcinoma, a type of cancer.

**Why Each Wrong Option is Incorrect**
**Option A:** Cardiac ischemia typically presents with a more acute onset of chest pain, often radiating to the arm, neck, or jaw, and is not usually exacerbated by meals or relieved by antacids.

**Option C:** A Mallory-Weiss lesion is a mucosal tear at the junction of the esophagus and stomach, often caused by intense or prolonged vomiting, retching, or coughing, and is not a direct consequence of GERD.

**Option D:** Squamous cell carcinoma is a type of esophageal cancer that arises from the squamous epithelium of the esophagus, which is not directly associated with GERD or columnar metaplasia.

**Clinical Pearl / High-Yield Fact**
It's essential to recognize that GERD is a chronic condition that can lead to complications such as columnar metaplasia and esophageal adenocarcinoma. Patients with symptoms of GERD should be regularly monitored for signs of Barrett's esophagus, and those with this condition should be referred for endoscopic surveillance.

**✓ Correct Answer: B. Columnar metaplasia of the distal oesophagus**