Black hairy tongue is a relatively uncommon condition characterized by a black or brown discoloration of the tongue’s dorsum, accompanied by a hairy or furry appearance due to elongation of the papillae. Squamous cell carcinoma (SCC) of the esophagus is a malignant neoplasm that arises from the esophageal epithelium. Several studies have suggested an association between black hairy tongue and squamous cell carcinoma of the esophagus.

The Association between Black Hairy Tongue and SCC of the Esophagus

Several case reports and case-control studies have suggested an association between black hairy tongue and SCC of the esophagus. In a case-control study conducted in the United States, researchers found that patients with black hairy tongue were more likely to develop SCC of the esophagus than those without black hairy tongue.

The odds ratio for SCC of the esophagus in patients with black hairy tongue was 7.4, indicating a significant association between the two conditions. Another case-control study conducted in Iran also found a significant association between black hairy tongue and SCC of the esophagus.

Mechanisms behind the Association

The exact mechanisms behind the association between black hairy tongue and SCC of the esophagus are not fully understood. However, several hypotheses have been proposed. One hypothesis is that the bacteria and fungi that colonize the tongue in patients with black hairy tongue produce carcinogenic substances that can promote the development of SCC of the esophagus.

Another hypothesis is that the elongated papillae in black hairy tongue can act as a reservoir for these carcinogenic substances, allowing them to accumulate and reach the esophagus.

Another possible mechanism is that the bacteria and fungi in black hairy tongue can increase the production of nitrosamines, which are known carcinogens. Nitrosamines are produced from nitrates, which are found in high concentrations in certain foods, such as processed meats.

The bacteria and fungi in black hairy tongue can convert nitrates to nitrites, which can then be converted to nitrosamines by stomach acid. Nitrosamines can promote the development of SCC of the esophagus by causing DNA damage and inducing mutations in the esophageal epithelium.

Conclusion

Black hairy tongue is a benign condition that is often asymptomatic and self-limited. However, several case reports and case-control studies have suggested an association between black hairy tongue and SCC of the esophagus. The exact mechanisms behind this association are not fully understood, but several hypotheses have been proposed. Further research is needed to elucidate the mechanisms behind this association and to determine if there is a causal relationship between black hairy tongue and SCC of the esophagus. Healthcare professionals should be aware of this association and consider SCC of the esophagus in the differential diagnosis of patients with black hairy tongue.