In this video blog, Dr. Ash Marghoob summarizes his lectures, Dermoscopy of Special Sites: Face, Hands and Feet, Nails, and Mucous Membranes , given on November 9, 2024, at 5th Annual Elevate-Derm West Conference at the Westin Kierland Resort in Scottsdale, AZ.

In this video

Dr. Marghoob explains that "special sites" earn the label because their micro-anatomy differs from the rest of the cutaneous surface — and, crucially, because the melanocyte stem cell (the origin of melanoma) sits in a different location. On facial skin the stem cell resides in the hair bulge, so early lentigo maligna features are perifollicular: asymmetric follicular openings, granularity, and linear projections around the hair follicle that later progress to angulated lines, rhomboids, and blotches. On palms and soles the stem cell lives in the acrosyringium, which opens on the ridge, so a ridge (parallel-ridge) pattern points to melanoma while pigment confined to the furrows reflects nevus cells growing in the rete ridges of the furrow. He notes the ink test is rarely needed since the wider ridge and white acrosyringeal openings usually distinguish the two.

For nails, Dr. Marghoob divides pigmentation into melanocytic activation (grayish/tan, homogeneous, no individual striations, arising from the lunula) versus proliferation (nevus vs. melanoma, individual striations, entire lunula pigmented). Regular, evenly spaced, parallel striations suggest a nevus; irregular lines with "disruption in parallelism" suggest melanoma. He stresses that four clinical clues — a triangular band wider at the base, involvement of more than half the nail, associated nail dystrophy, and Hutchinson sign — trump any dermoscopic finding and warrant biopsy. On mucosal surfaces, where robust data is still lacking, he emphasizes color above all: blue, gray, or white is the most sensitive feature for melanoma (roughly 100% sensitivity, 64% specificity), while a single brown color favors a benign lesion.

  • The face, palms/soles, nails, and mucosa are "special sites" because their micro-anatomy — and the location of the melanocyte stem cell — differs from the rest of the skin.
  • Early lentigo maligna is perifollicular: asymmetric follicular openings, granularity, and linear projections that later form angulated lines and rhomboids.
  • On palms and soles, a ridge pattern (pigment on the wider ridge with acrosyringeal openings) suggests melanoma; pigment confined to the furrows suggests a nevus. The ink test is rarely needed.
  • In nails, regular parallel striations favor a nevus while "disruption in parallelism" favors melanoma — but a triangular band, involvement of over half the nail, nail dystrophy, or Hutchinson sign trump dermoscopy and warrant biopsy.
  • For mucosal lesions, color is the key clue: blue, gray, or white is the most sensitive feature for melanoma, whereas a single brown color favors a benign lesion.