Lentigines (Lentigo)

Definition/Appearance

• A lentigo is a small, pigmented, flat/slightly raised spot with a clearly defined edge, surrounded by normal skin
• They can appear slowly over years or more suddenly
• They can appear anywhere on the body and can vary in colour from light/tan brown to black.
• There are several types
  • Lentigo simplex (most common)
    • Usually appear at birth/early childhood; not associated with sun exposure (cf ephelides/true freckles); typically 5-15mm and dark
  • Solar lentigo (‘age-spots’ or ‘liver-spots)
    • Sun-induced lesion (appears on face, arms, hands); usually pale tan/pink  (can be darker) and <5mm although they may coalesce to form larger lesions; tends to appear in middle age (30-50) and most commonly seen in older individuals
  • Ink-spot lentigo
    • Resembles spot of ink (wiry/beaded irregular outline); occurs in sun-exposed areas, commonly surrounded by solar lentigines and most common in people of Celtic-origin.  Often hard to distinguish from melanoma
  • PUVA lentigo
    • Persistent, pale to dark brown macule appearing 6 months or more after the start of PUVA treatment.  Similar to solar lentigines but usually irregularly bordered.
  • Other types include radiation lentigo (associated with large radiation doses e.g. seen after chernobyl disaster); tanning bed lentigo (associated with tanning bed use); oral/labial (found on lips/mouth); genital lentigo; generalised lentigines (lentigines profusa- widespread multiple lesions of idiopathic origin); agminated lentiginosis (associated with other childhood diseases; distributed in a sharply demarcated region e.g. dermatomes)
• May be associated with other systemic conditions e.g. LEOPARD; Peutz-Jeghers syndrome; Laugier-Hunziger syndrome; Myxoma syndromes e.g. LAMB; NAME and Carney’s syndrome

NB Lentigo maligna is a precancerous condition not discussed here

Investigations, Management

• If concerned about diagnosis e.g. melanoma, skin biopsy is appropriate
• If the patient is concerned about appearance, nitrogen therapy may lighten the lesion
• Reassurance is mainstay- no treatment required

Histology

• Increased proliferation of normal melanocytes, such that they replace the keratinocytes at the basal layer