Brown Spot on Tongue: Diagnosis and Management
A long-standing brown spot on the tongue is most likely a benign melanotic macule, which requires no treatment but warrants clinical examination to exclude malignancy, particularly in patients over 40 years with tobacco or alcohol use.
Differential Diagnosis
The most common causes of a brown spot on the tongue include:
- Melanotic macule (most likely): Benign pigmented lesions that can be congenital or acquired, appearing as smooth brown macules measuring several millimeters, particularly common in dark-skinned individuals 1
- Oral melanoma or pigmented squamous cell carcinoma: Must be excluded, especially with concerning features 2
- Amalgam tattoo: From dental materials, typically near dental work 3
- Physiologic pigmentation: Normal variant in darker-skinned populations 3
Key Clinical Assessment
High-Risk Features Requiring Urgent Evaluation
Examine for signs that increase suspicion for malignancy 2:
- Patient factors: Age >40 years, tobacco use, alcohol abuse, immunocompromised status 2
- Lesion characteristics: Change in symmetry, border irregularity, color variation, diameter increase, or ulceration 2
- Associated symptoms: Limited tongue mobility (suggests muscle/nerve invasion), new numbness, dysphagia, odynophagia, weight loss, hemoptysis, or blood in saliva 2
- Physical findings: Ulceration, induration, fixation to underlying structures, or palpable neck lymphadenopathy 2
Critical Examination Technique
- Tongue inspection: Use gauze to grasp and extend the tongue to visualize lateral aspects thoroughly, as limited tongue mobility may indicate tumor invasion 2
- Palpation: Palpate the oral tongue, base of tongue, and neck for masses; nontender neck masses are more suspicious for malignancy than tender ones 2
- Lesion assessment: Determine if the lesion is flat (macule) versus raised, smooth versus irregular, and whether it has changed over time 2, 1
Management Algorithm
For Benign-Appearing Lesions (No High-Risk Features)
- Observation is appropriate for stable, asymptomatic brown macules without concerning features, particularly congenital lesions identified in infancy or childhood 1
- Clinical follow-up: Monitor for any changes in size, color, or symptoms 1
- Patient reassurance: Congenital lingual melanotic macules represent a clinically distinct and benign cause of hyperpigmentation 1
For Lesions with ANY Concerning Features
Biopsy is mandatory for 4:
- Lesions persisting beyond 2 weeks despite observation
- Any change in appearance (asymmetry, border, color, diameter)
- Unilateral lesions in high-risk patients
- Non-scrapable lesions
- Associated ulceration or induration
Pre-Biopsy Workup
Before performing biopsy, obtain 4:
- Complete blood count (to exclude anemia, leukemia)
- Coagulation studies
- Fasting blood glucose
- HIV antibody testing
- Syphilis serology
Critical Pitfalls to Avoid
- Never assume all pigmented tongue lesions are benign: Failure to biopsy persistent, non-scrapable, or unilateral lesions in high-risk patients can delay cancer diagnosis 5
- Do not overlook examination of the entire oral cavity: Remove dentures and examine all mucosal surfaces, as oral cancers can present with referred tongue symptoms 2
- Avoid incomplete examination: If the base of tongue cannot be visualized without flexible laryngoscopy, refer to a specialist rather than assuming the lesion is isolated 2
- Do not dismiss lesions based solely on duration: While long-standing lesions are more likely benign, melanoma and other malignancies can be slow-growing 2, 1
When to Refer
Immediate referral to oral and maxillofacial surgery, head and neck surgery, or dentist experienced in oral pathology is indicated for 2, 3:
- Any lesion with high-risk features or concerning examination findings
- Inability to complete adequate examination of the tongue base and oropharynx
- Lesions of unclear etiology after initial assessment
- Patients with history of prior head and neck malignancy