In cases of squamous cell carcinoma of the esophagus, what is a primary risk factor?

Smoking is a well-established primary risk factor for the development of squamous cell carcinoma of the esophagus. This type of cancer is more common in populations with high tobacco use due to the carcinogenic compounds found in tobacco, which can lead to genetic mutations in the cells lining the esophagus.

While chronic reflux disease, or gastroesophageal reflux disease (GERD), is more commonly associated with adenocarcinoma of the esophagus, smoking has a more direct correlation with squamous cell carcinoma. Similarly, obesity has also been recognized as a risk factor for esophageal adenocarcinoma, but it is less directly related to squamous cell carcinoma. Therefore, among the options given, smoking stands out as the primary risk factor specifically linked to squamous cell carcinoma of the esophagus.