Chapter 19: Nail Melanoma

SUMMARY

• Nail melanoma can originate from the nail matrix (typically with longitudinal melanonychia) or the nail bed (typically amelanotic).

• Nail melanoma is more common in ethnicities with darker skin, such as Native Americans, Africans, and Hispanics.

• While clinical findings and dermoscopy can help narrow a differential, pathology is the only way to confirm diagnosis of nail melanoma.

TIPS FOR DIAGNOSIS

• Remember your ABCDEF of nail melanoma: Age and Race (40–60 yrs; e.g., African, Asian, Hispanic), Border (border irregularities and/or Hutchinson’s sign), Color (variation in color), Digit (melanonychia located on fingernails; single finger nail; thumb), Evolution (changes in shape, color, or size), and Familial History (family and personal history of skin cancer).

• The gold standard for diagnosis of nail melanoma diagnosis is a full thickness, tangential excision of the entire pigmented nail matrix or nail bed lesions.

TIPS FOR TREATMENT

• A more conservative approach for in situ nail melanoma is recommended with an approximate 5-mm wide margin resection of nail apparatus.

• Invasive subungual melanoma treatment involves amputation of the distal phalanx, sentinel lymph node biopsy, and oncologic referral.

DON’T FORGET

• While longitudinal melanonychia is one of the most common clinical findings for nail melanoma, recall that up to 25% of cases are amelanotic.

• Nail melanoma is exceptional in children, with less than 20 cases reported in the literature.

PITFALLS AND CAUTIONS

• To reduce a missed diagnosis, ensure that the full thickness biopsy includes a wide resection margin and contains parts of the nail bed, nail plate, and nail matrix.

• History of a previous trauma does not exclude diagnosis of melanoma as this is reported in up to 40% of cases.

EXPERT PEARLS

• Experts recommend examination of longitudinal melanonychia every 6 months for lesions that have no suspicious findings.

• Baseline photography and dermoscopy should be used at initial visit and every subsequent follow-up to accurately document changes.

PATIENT EDUCATION POINTS

• Patients should be educated about performing skin self-exams after a bath or shower; specify the importance of examining from head-to-toe and likewise examining each nail individually.

• Patients with melanocytic activation should be educated about regularly checking their nails and following up with a dermatologist if noticing any irregular changes in color, size, or shape.