What are the potential causes of tongue cancer in a person with no history of alcohol consumption or tobacco use?

Causes of Tongue Cancer in Non-Smokers and Non-Drinkers

In someone who never smoked or drank alcohol, tongue cancer is most likely caused by chronic dental trauma/irritation, HPV infection (though less common in oral cavity than oropharynx), genetic susceptibility, or remains idiopathic despite investigation. 1, 2

Primary Risk Factors to Consider

While tobacco and alcohol account for 75-85% of head and neck cancers overall, 15-25% of oral cavity cancers occur in never-smokers/never-drinkers, representing a distinct clinical entity 1, 3.

Chronic Dental Trauma (Most Important for Oral Tongue)

• Oral cancers in non-smokers occur predominantly at sites of potential dental trauma, particularly the lateral tongue (66% of non-smokers vs. 33% of smokers, p<0.001) 2
• Chronic irritation from:
  • Sharp or broken teeth rubbing against tongue
  • Ill-fitting dentures (especially gingival/floor of mouth lesions in elderly patients) 1, 2
  • Dental abnormalities in close proximity to tumor development 2
• This represents a potentially modifiable risk factor that is often overlooked

HPV Infection

• HPV is primarily associated with oropharyngeal cancer (30-35% of cases), NOT oral cavity/tongue cancer 1
• HPV-positive squamous cell carcinoma outside the oropharynx is rare (<6%) 1
• More than half of non-smoker/non-drinker patients with oropharyngeal primaries test positive for HPV-16, but this does not extend to oral tongue cancers 3
• Studies specifically searching for oncogenic viruses in oral tongue cancer of non-smokers found no tumor-associated viruses detected 4

Secondary Risk Factors

Environmental and Occupational Exposures

Among never-smoker/never-drinker patients with head and neck cancer 3:

• 41% (45% of women) reported regular environmental tobacco smoke exposure
• 24% (36% of men) reported occupational carcinogen/toxin exposures
• 11% (17% of men) used non-cigarette tobacco products or marijuana

Other Recognized Risk Factors 1

• Radiation exposure (prior therapeutic radiation)
• Chronic infection and poor oral hygiene
• Long-term immunosuppression (transplant patients, HIV)
• Poor nutrition (micronutrient deficiency accounts for 10-15% of oral cancers worldwide) 5
• Betel nut chewing (>50% of oral cancers in high-prevalence areas)
• Gastroesophageal reflux disease (30% of non-smoker/non-drinker patients) 3

Genetic Predisposition

Consider genetic counseling if 1:

• Young age at presentation (<40-45 years)
• Cytopaenia present
• Family history of multiple cancers
• Absence of other risk factors

Rare inherited syndromes include:

• Fanconi anemia
• Ataxia telangiectasia
• Bloom's syndrome
• Li-Fraumeni syndrome
• Dyskeratosis congenita

Specific polymorphisms in carcinogen-metabolizing enzymes (GSTM1, GSTT1, EPHX1) have been associated with increased risk 1.

Clinical Patterns in Non-Smokers/Non-Drinkers

Three distinct subgroups emerge 3, 6:

1. Young women with oral tongue cancer (most common pattern)

   • Significantly younger than smokers (mean age 50.4 vs 61.9 years, p<0.001) 3
   • More likely female (58.5% vs 38.9% in smokers) 3
   • Lateral tongue predominance suggests dental trauma etiology 2

2. Elderly women with gingival/buccal cancer

   • Likely related to chronic denture irritation 2

3. Young to middle-aged men with oropharyngeal cancer

   • More likely HPV-related 3

Molecular Differences

Non-smokers have fewer TP53 mutations than smokers (p=0.02), suggesting different carcinogenic pathways 4, 7. The absence of p53 mutations in young non-smoking patients indicates that the molecular mechanism differs fundamentally from tobacco/alcohol-induced carcinogenesis 7.

Critical Clinical Caveat

Despite thorough investigation, no single known factor is responsible for the majority of head and neck cancers in never-smokers/never-drinkers 3. Many cases remain idiopathic, highlighting the need for continued research into novel risk factors and carcinogenic mechanisms in this population.