Melanoma

Figure 5.10 A: Lentigo maligna* B: Melanoma C: Hutchinson’s sign* *Courtesy of Dr. Paul Getz

Figure 5.11 Melanoma (Courtesy of Dr. Paul Getz)

• Aggressive tumor resulting from melanocytes and affecting younger population (peak age 20–45 years old)
• Risk factors: tendency to sunburn/freckle, light-colored skin/hair/eyes, several nevi, CDKN2A mutation, prior history of melanoma, intermittent high UVR with sunburns in childhood/adolescence, immunosuppression (transplant patients with threefold to fourfold higher risk)
• Four clinical types:
  • Superficial spreading melanoma (SSM): most common (70% in white population); presents as darkly pigmented macule or thin plaque, ± notched border, varying shades of brown, possible areas of regression; most common site is back (men) and lower legs (women); horizontal growth
  • Nodular melanoma (NM): second most common type in light-skinned patients, darkly pigmented papule or nodule with rapid onset; vertical growth
  • Lentigo maligna melanoma (LMM): least common; evolves from lentigo maligna, often in sun-exposed sites in older age group; presents as hyperpigmented patch with varying shades of brown, irregular border
  • Acral lentiginous melanoma (ALM): most common type seen in darker-skinned patients; often presents as hyperpigmented patch with varying shades of brown or black and irregular borders
• Histology: asymmetric, poorly circumscribed collection of atypical melanocytes; single melanocytes characteristic and often with pagetoid spread, irregular nests in basal layer and invasion into the dermis, poor maturation of melanocytes, ± regression
• Recent guidelines emphasize tumor mitotic rate (TMR) and have incorporated this into existing staging system
• Poor prognostic factors: male gender, increasing age, increased tumor thickness, ulceration, increased TMR, and head/neck/trunk location (vs. extremities)
• Treatment: conventional excision with margins, Mohs micrographic surgery, ± sentinel lymph node biopsy (usually for intermediate thickness melanoma of 1–4 mm); advanced cases: interferon-α, interleukin-2, chemotherapy/radiation therapy, vaccine therapy
  • Excision margins for melanoma:
  • Melanoma in situ: 0.5 cm margins
  • Melanoma <2 mm: 1 cm margins
  • Melanoma ≥ 2 mm: 2 cm margins