Structured Approach to Melanonychia
1. History Taking
Patient Information
- Demographics:
- Sex and age: Subungual melanoma mostly occurs between the ages of 50 and 70 years.
- Duration:
- Time since the onset of symptoms.
- Note if the onset was sudden or gradual.
- Location:
- Specific nails affected.
- Whether the condition affects fingernails, toenails, or both.
- Changes in Pigmentation:
- Any changes in color (from light brown to black).
- Changes in the width of the pigmented bands.
- Symptoms:
- Presence of nail pain or bleeding.
- Nail deformity or fragility.
- Occupation:
- Consider any occupational exposures (e.g., chemicals, trauma) that might contribute.
- Trauma:
- Any history of trauma to the nails.
- Family History:
- Family history of melanoma or other skin cancers.
- Medical History:
- Previous medical conditions and their treatments.
- History of conditions like acquired immunodeficiency syndrome (AIDS), which can affect nail pigmentation.
- Drug History:
- Current and past medications, as certain drugs (e.g., chemotherapeutic agents, antimalarials) can cause benign melanonychia.
- Female Patients:
- History of pregnancy and its relation to the onset or progression of longitudinal melanonychia.
- Changes during pregnancy can affect nail pigmentation.
2. Physical Examination
General Nail Assessment
- Observation:
- Gross examination of all fingernails and toenails.
- Involvement:
- Number of nails affected.
- Whether the condition is limited to one nail or multiple nails.
- Pigmented Bands:
- Note the color (brown to black) and width of the pigmented bands.
- Monitor any changes over time.
- Skin Involvement:
- Check for involvement of the eponychium, hyponychium, or lateral grooves.
Detailed Characteristics
- Location of Pigmented Streaks:
- Determine if they are on top of, within, or beneath the nail plate.
- Pattern:
- Check if pattern of melanonychia—complete, longitudinal, or
- transverse.
- Proximal Changes:
- Look for streaks that are wider or darker proximally.
- A trapezoid-like shape with a wide proximal bottom and narrow distal top may indicate melanocytic hyperplasia.
- Nail Plate Dystrophy:
- Assess for any dystrophy (splitting, ridging) or deformity of the nail plate.
Hutchinson’s Sign
- Assessment:
- Check for the extension of pigmentation into the skin and soft tissue surrounding the nail plate (eponychium, hyponychium, lateral grooves).
- Hutchinson’s sign is considered almost pathognomonic of subungual melanoma.
- Mimickers:
- Laugier-Hunziker syndrome.
- Congenital nevi of the nail unit.
- Radiation therapy.
- Malnutrition.
- Ethnic nail pigment changes, especially in dark-skinned individuals.
- Acquired immunodeficiency syndrome (AIDS).
- Drug intake.
- Regressive nevoid nail melanosis in Japanese children.
- Pseudo-Hutchinson’s Sign:
- Especially in children, where thinner periungual skin can show pigmentation that mimics true Hutchinson’s sign.
3. Dermoscopy
Melanin Pigmentation
- Examination:
- Use dermoscopy to examine the melanin pigmentation.
- Differentiate melanin from blood spots and exogenous substances (dirt, tar, tobacco).
- True vs. Pseudo-Hutchinson’s Sign:
- Identify whether the pigmentation is within the skin of the proximal nail fold (pseudo-Hutchinson’s sign) or extending into the surrounding skin (true Hutchinson’s sign).
Patterns
- Benign Features:
- Regular, parallel lines of uniform color and width.
- Malignant Features:
- Irregular lines in color, width, and spacing.
- Loss of parallelism.
- Irregular patterns and pseudo-Hutchinson’s sign in children suggest more melanoma-associated features.
4. Biopsy
Indications
- Suspicious Changes:
- Sudden or rapid changes in the width or color of pigmented bands.
- Border Characteristics:
- Blurred or irregular borders.
- Color:
- Irregular color within the band.
- Nail Deformity:
- Presence of nail plate deformity or dystrophy.
- Wide Bands:
- Especially solitary black streaks in white individuals.
- Nail Plate Dystrophy:
- Changes in the nail plate such as splitting, ridging.
Procedure
- Punch Biopsy:
- Perform a 2- to 3-mm punch biopsy at the proximal part of the streaks and the distal part of the nail matrix.
- Specimen removed directly through the nail plate to the underlying bone.
- Management:
- Careful management post-biopsy to minimize the risk of nail deformity or dystrophy.
5. Surgical Excision
Indications
- Adult Patients:
- Especially those over 50 years of age.
- Rapid Changes:
- Rapid or sudden increase in the width of the pigmented band.
- Size and Borders:
- Width over 5 mm or blurred borders.
Procedure
- Excision:
- Complete excision of the suspicious pigmented bands from the nail matrix to the distal hyponychium.
- Incision:
- Make a skin incision through the entire width of the proximal fold of the eponychium.
- Nail Plate Removal:
- Carefully remove the nail plate to visualize and locate the nevus and pigmented streaks.
- Tapered Excision:
- Perform a tapered pointed excision to remove the pigmentation, avoiding the proximal part of the nail matrix.
- Margins:
- Include 1- to 2-mm lateral margins in the excised specimen.
- Tangential Excision:
- A shallow incision through the matrix epithelium and papillary dermis around the identified pigmented lesion.
- Lower incidence of nail deformity but a higher recurrence of pigmentation.
Post-Surgery
- Histological Examination:
- Further section and examine the excised specimens.
- Referral:
- Refer to a cancer center for further treatment if pathology indicates malignancy.
- Monitoring:
- Monitor for recurrence, particularly in cases of large or total melanonychia.
- Over two-thirds of patients who underwent surgery had no recurrence.
ABCDEF Rule
- Age and Ethnicity:
- Higher risk in older patients (50-70 years) and certain ethnic groups.
- Band Characteristics:
- Wide (≥3 mm), brown to black, with irregular borders.
- Change:
- Rapid increase in size or change in morphology of the band.
- Digit Involvement:
- Thumb, hallux, index finger, single digit, and dominant hand are higher risk.
- Extension:
- Hutchinson’s sign (pigment spread to periungual skin).
- Family History:
- Personal or familial history of dysplastic nevi or melanoma.
Imaging
- Ultrasound and MRI:
- Helpful in diagnosing melanonychia due to nail tumors and delineating lesion extent.
Differential Diagnoses
- Fungal melanonychia.
- Exogenous pigmentation.
- Subungual hematoma.
- Other nail disorders have similar presentations.