I have a black pigmented lesion on my tongue; what could be causing it and how should it be evaluated and managed?

Black Spot on Tongue: Evaluation and Management

A black pigmented lesion on the tongue is most commonly benign black hairy tongue (lingua villosa nigra), but requires systematic evaluation to exclude serious conditions including oral melanoma, medication-induced pigmentation, and systemic diseases.

Immediate Diagnostic Approach

First-Line Clinical Assessment

Determine if the lesion is macular (flat) or raised, and assess the surface texture:

• Black hairy tongue presents with elongated, hypertrophied filiform papillae creating a "hairy" appearance on the dorsal tongue surface, typically brownish-black in color 1, 2
• Smooth, macular pigmentation without papillary hypertrophy suggests medication-induced pigmentation, physiologic melanosis, or more concerning pathology 3, 2
• Raised or nodular lesions require urgent biopsy within 2 weeks to exclude melanoma, particularly if located on the lateral tongue 4

Critical Red Flags Requiring Urgent Biopsy (Within 2 Weeks)

Any of the following features mandate tissue diagnosis:

• Non-homogeneous appearance with mixed pigmentation 5
• Progressive growth over observation period 6, 4
• Ulceration or spontaneous bleeding 6, 4
• Indurated or fixed mass 4
• Location on lateral tongue or floor of mouth (high-risk sites for malignancy) 5
• Patient age >40 years with tobacco or alcohol use 4, 5
• Persistent lesion >2-3 weeks without identifiable benign cause 6, 5

Differential Diagnosis by Clinical Presentation

Benign Black Hairy Tongue (Most Common)

Characterized by elongated filiform papillae with dark discoloration:

• Caused by overgrowth of dead skin cells, accumulation of bacteria, fungi, food debris, and pigments 7, 1
• Associated with poor oral hygiene, soft diet, smoking, antibiotics, and bismuth-containing medications 3, 1
• Typically asymptomatic but may cause bad breath and metallic taste 8
• Management: Gentle tongue brushing or scraping twice daily, eliminate predisposing factors (discontinue causative medications, improve oral hygiene), and observe for resolution within 2-4 weeks 7, 1

Medication-Induced Macular Pigmentation

Smooth tongue surface without papillary hypertrophy:

• Bismuth subsalicylate (Pepto-Bismol) causes transient black pigmentation that resolves within hours to days after discontinuation 3
• Other medications include antimicrobials, antidepressants, antihypertensives, and chemotherapy agents (doxorubicin, interferon) 3
• Onset varies from <1 day to several years after initial exposure 3
• Management: Discontinue suspected medication and observe for resolution; pigmentation typically resolves after agent is stopped 3

Physiologic or Systemic Causes

Consider in patients with darker skin or systemic disease:

• Physiologic melanosis more common in individuals with dark skin 2
• Systemic diseases including Peutz-Jeghers syndrome (mucocutaneous pigmentation with GI polyposis), Addison's disease, or autoimmune conditions 9, 8
• Peutz-Jeghers presents with dark brown or blue-brown macules 1-5mm in size on buccal mucosa (66% of patients), typically appearing in infancy 9

Amalgam Tattoo

Localized blue-gray to black pigmentation:

• Results from traumatic implantation of dental amalgam into oral mucosa 2
• Typically occurs near dental restorations 2
• Biopsy indicated if diagnosis uncertain based on clinical presentation 2

Management Algorithm

For Lesions with Benign Features (No Red Flags)

Step 1: Document lesion size, exact location, and obtain photographic evidence if possible 5

Step 2: Review medication history and identify potential causative agents (bismuth products, antibiotics, other medications) 3

Step 3: If black hairy tongue suspected, initiate gentle tongue brushing twice daily and eliminate predisposing factors 7, 1

Step 4: Observe for 2-3 weeks with patient counseling on tobacco/alcohol cessation if applicable 6, 5

Step 5: Re-evaluate at 2-3 weeks; if no improvement or any change in appearance, proceed to biopsy 6, 5

For Lesions with Any Red Flag Features

Immediate referral to oral surgery or oral medicine specialist for biopsy within 2 weeks 4, 5

• Incisional biopsy required for persistent lateral tongue lesions, particularly if non-homogeneous 5
• Pre-biopsy evaluation includes complete blood count, coagulation studies, and fasting blood glucose 5
• Do not delay biopsy for empiric treatment trials 5

Critical Pitfalls to Avoid

Never assume a lateral tongue pigmented lesion is benign without histologic confirmation - the lateral tongue is a high-risk site for oral squamous cell carcinoma 5

Do not delay biopsy for empiric antifungal treatment - if candidiasis suspected, attempt to scrape the lesion first; persistent lesions after 2 weeks require biopsy 5

Avoid over-treatment of benign black hairy tongue - aggressive interventions are unnecessary and can cause morbidity 6

Do not rely on clinical appearance alone to distinguish between benign pigmentation, leukoplakia, and early malignancy - histopathology is essential for definitive diagnosis 5

Follow-Up Protocol

• Re-evaluate all lesions under observation at 2-3 weeks 6
• Any lesion persisting beyond observation period requires referral for biopsy 6, 5
• Patients with systemic disease or immunosuppression require closer monitoring 6
• Black hairy tongue typically resolves within 2-4 weeks with appropriate tongue hygiene 7, 1