Lentigines

A lentigo is a well circumscribed, uniformly pigmented macule caused by an increase in the number of melanocytes along the basal layer of the epidermis, so it does not fade with sun avoidance (unlike a freckle).

• Main types:
  • Solar lentigo (age spot, liver spot): from chronic ultraviolet exposure. It affects more than 90% of fair skinned people over 60 years.
  • Lentigo simplex: onset in childhood, not sun related, on any site including mucosa, common and benign.
  • Ink spot lentigo: dark black, irregular bordered, in people with sun sensitive skin and sunburn history.
  • PUVA and sunbed lentigines: after psoralen with UVA phototherapy or tanning bed use, which may indicate increased skin cancer risk.
  • Mucosal lentigines: lips, oral and genital mucosa.
  • Lentigo maligna: melanoma in situ on chronically sun damaged skin of the head and neck, which can progress to invasive lentigo maligna melanoma. It is the malignant counterpart that must be excluded.
• Syndromic lentiginoses: Peutz-Jeghers syndrome (STK11, with intestinal hamartomatous polyps and cancer risk), LEOPARD syndrome (PTPN11, with cardiac, ocular, genital, growth and hearing abnormalities), Carney complex (PRKAR1A, with cardiac myxomas and endocrine tumours), Laugier-Hunziker syndrome (benign, mucosal and nail pigmentation), and other rare conditions.

• Solar lentigo: well demarcated, round or oval, uniformly tan to dark brown macule, 5 mm to more than 3 cm, with a smooth or slightly irregular border, on the face, dorsal hands, forearms, shoulders, upper back and bald scalp. Lesions are flat, with no scale (unless a seborrhoeic keratosis has developed).
• Lentigo simplex: 1 to 5 mm brown to black macule with a sharp border, often scattered and not sun related.
• Peutz-Jeghers syndrome: 1 to 5 mm brown to blue grey macules around the mouth, lips, nostrils, eyes, hands, feet and buccal mucosa, appearing in infancy and fading on the skin in adult life (mucosal lesions persist). It is accompanied by recurrent abdominal pain, intussusception, gastrointestinal bleeding and anaemia.
• Lentigo maligna: an enlarging, irregular, asymmetrical macule with colour variation (brown, black, grey, pink) on the face of an older person. Development of a nodule, ulceration, or bleeding indicates invasion.
• Differential diagnosis: seborrhoeic keratosis (flat, waxy, stuck on), actinic keratosis (rough scale), junctional or lentiginous naevus, lentigo maligna and melanoma, pigmented basal cell carcinoma, melasma, post-inflammatory hyperpigmentation, café-au-lait macules, and freckles.
• Complications: cosmetic concern, misdiagnosis of lentigo maligna, and in the syndromic forms the complications of the underlying disease.

• Clinical examination with dermoscopy. Features of a benign solar lentigo: sharply demarcated edge ("moth eaten" or scalloped), uniform light brown colour, and fingerprint like or "cerebriform" structures if it has become a seborrhoeic keratosis.
• Features suggesting lentigo maligna: asymmetric pigmented follicular openings, annular granular pattern, rhomboidal structures, grey dots, and obliteration of follicles. Reflectance confocal microscopy helps in specialist centres.
• Biopsy for any lesion with asymmetry, colour variation, growth or a suspicious dermoscopic pattern. Use a full thickness incisional or excisional sample, as a small punch may miss the diagnosis.
• Syndromic lentiginosis: clinical genetics referral, and genetic testing for STK11, PTPN11, PRKAR1A and others as suggested by the features.
  • Peutz-Jeghers syndrome: small bowel and colon surveillance from about 8 years of age, repeated every 1 to 3 years depending on the polyp burden, with removal of polyps larger than 1 cm to prevent intussusception. Screening for breast, pancreatic, gynaecological and testicular tumours is started in adult life (evidence is limited).
  • LEOPARD syndrome: electrocardiogram and echocardiogram, hearing and growth review.
  • Carney complex: echocardiogram, and endocrine tests (insulin like growth factor 1, cortisol, thyroid ultrasound).

• Benign solar and simple lentigines need no treatment. Reassure, and advise sun protection and monitoring.
• Photoprotection: sunscreen SPF 50, broad spectrum, daily, with a hat and protective clothing, and no tanning devices.
• Cosmetic removal on request:
  • Cryotherapy with liquid nitrogen, 5 seconds, 1 freeze thaw cycle. A crust forms and falls in 1 to 2 weeks, with a risk of hypopigmentation and recurrence (higher risk in dark skin, so use a shorter time).
  • Topical tretinoin 0.05 to 0.1% cream nightly for 3 to 6 months, hydroquinone 4% twice daily for 8 to 12 weeks, or a triple combination cream (hydroquinone 4%, tretinoin 0.05%, fluocinolone acetonide 0.01%) nightly for 8 weeks.
  • Chemical peels (glycolic acid 30 to 50%, trichloroacetic acid 15 to 25%) at 2 to 4 week intervals.
  • Q-switched 532 nm Nd:YAG, ruby or alexandrite lasers, or intense pulsed light (2 to 3 sessions), with the best results in fair skin and a risk of post-inflammatory pigmentation in dark skin.
  • Biopsy before treating any lesion where lentigo maligna is a possibility.
• Lentigo maligna and lentigo maligna melanoma:
  • Surgical excision with a margin of 5 to 10 mm (wider margins or staged excision, or Mohs micrographic surgery, in the head and neck to ensure clearance).
  • Imiquimod 5% cream, 5 nights per week for 8 to 12 weeks (off label, with higher recurrence), or radiotherapy, for patients who are unfit for or decline surgery.
  • Refer urgently to dermatology or plastic surgery if invasion is suspected. Invasive melanoma needs staging and management by a melanoma team.
• Syndromic disease: multidisciplinary care, periodic skin and systemic surveillance for associated tumours, and counselling of the family.
• Special groups:
  • Pregnancy: sun protection. Defer retinoids, hydroquinone, peels and lasers.
  • Dark skin: choose gentler treatments, and test a patch.
  • Transplant recipients and other immunosuppressed patients: examine the skin every 6 to 12 months, with a low threshold for biopsy.
• Follow up: yearly skin examination for sun damaged skin. Reassess any lesion that grows, changes in colour or shape, bleeds or becomes raised.