Structured Approach to Melanonychia

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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.

References


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