Lentigo

Lentigines (pleural of lentigo) are flat brown lesions which do not darken following sun exposure (thus differentiating them from ephelides or true freckles). They may be any size from 5-20mm, and may be irregular in shape. They occur over the shoulders in young people, especially those who have had a lot of sun exposure, and in the elderly on the sun exposed sites such as dorsum of the hands and forearms, face and neck.
The histopathology may include hyperplasia of the epidermis and pigmentation of the basal layer.¹

A number of different types are found:¹

• Lentigo simplex - this is the commonest type, and seen mainly in children. The condition is not associated with sun exposure. The spots are 5-15mm in diameter.
• Solar lentigo - these are related to sun exposure and seen on areas of skin normally exposed to sunlight (e.g. face, hands). They are benign lesions, less than 5mm in diameter, but they may merge to form larger spots. The peak age used to be 30-50 but is getting younger with increasing sun exposure. The colour may vary from yellow-brown to black.
• Ink-spot lentigo - this lesion, so called because it resembles a spot of ink, is a benign lesion limited to sun-exposed areas. They are usually solitary lesions and may be mistaken for melanomas.
• PUVA lentigo - these brown macules can appear 6 months or more after the start of PUVA treatment for psoriasis in areas exposed to treatment. The macules are usually 3-8mm in diameter and persist for 3-6 months after treatment has finished. There is also a larger stellate form (which can be up to 3cm in diameter) which may persist for 2 years or more.
• Radiation lentigo - this appears after a single large exposure to radiation (of Chernobyl proportions rather than post-radiotherapy). There may be other histological signs of radiation damage such as epidermal atrophy and subcutaneous fibrosis. The malignant potential for such lesions is not known.
• Sun-bed lentigo - lentigines can appear rapidly after intense exposure, or they may appear after long-term use. The are 2-5mm in diameter and are commonest on the anterior aspects of the arms and legs.
• Labial and oral melanotic macules - labial macules usually appear as single lesions on the vermillion of the lower lip. Oral lesions occur on the gingival and buccal mucosa, palate and tongue.
• Genital lentigo - in men this can present as a tan to dark brown macule anywhere on the glans, shaft or corona. They can achieve a size of 15mm. In women, lentigenes can occur anywhere on the genital mucosa, and are usually between 5-15mm in size.
• Lentigenes profusa - in this condition there are widespread lentigens over the arms, legs and genitalia. There are no trigger factors or associated abnormalities (thus differentiating them from a number of lentigo-associated syndromes, see below). The lesions can be 5m-2cm in diameter. The appearance is of dark brown or black freckles, but with a more generalised distribution.
• Agminated lentiginosis - in this condition, which can be associated with a number of childhood diseases, lentigenes appear in a sharply demarcated distribution which often follow the outline of dermatomes. They are tan or dark brown in colour, and may be present at birth or develop in early childhood.

A number of lentigo-associated conditions can occur:¹

• LEOPARD - lentigines, electrocardiographic conduction defects, ocular hypertelorism, pulmonary stenosis, abnormal genitalia, retardation of growth, deafness
• Peutz-Jeghers syndrome - gastrointestinal polyps and pigmented macules
• Laugier-Hunziker syndrome - a variable number of pigmented macules appearing commonly around the oral mucosa or lower lip, and in other areas
• Myxoma syndromes - a group of disorders including:
  • LAMB - lentigines, atrial myxomas, mucocutaneous myxomas, and blue naevi
  • NAME - naevi, atrial myxoma, myxoid neurofibroma, and ephelides
  • Carney syndrome - cardiac, cutaneous, and mammary myxomatous masses; lentigines; blue naevi; endocrine disorders; and testicular tumors.

• Actinic Keratosis
• Ephelides (freckles) - get darker after sun exposure
• Seborrheic Keratosis
• Xeroderma pigmentosum - an autosomal recessive condition in which the DNA fails to repair itself after skin damage
• Melanoma - tend to have more variation in colour density within the lesion than a lentigo
• Lentigo maligna² - seen mainly on the sun-exposed areas of the face and neck in the elderly, is slow growing and usually quite large. (>20mm). Their size and site differentiates them from lentigenes. Lentigo maligna is a pre-cancerous condition. Conversion to a lentigo maligna melanoma can take from a few months to up to 15 years, and occurs in approximately 5% of patients. Identifying lesions that require referral is not easy, but worrying signs include changes in size or colour, itching, burning, bleeding, or pain. The ABCDE rule of melanoma may be helpful:
  • A - Asymmetry
  • B - Border irregularity
  • C - Colour variegation
  • D - Diameter greater than 6 mm (the end of a pencil head), although melanoma can occur in lesions less than 6 mm
  • E - Enlargement

• Unsightly lesions of face can be lightly frozen, which often improves the cosmetic result.
• New lesions can be prevented to some extent by sun avoidance, use of sunblock creams and keeping on a shirt when outside in the sunshine.

Lentigines tend to get worse over time, but do not go malignant.

• For doubt over diagnosis and for diagnostic biopsy.
• When treatment is required but cannot be provided within primary care - e.g. treatment with lasers (Q-switched ND-YAG or ruby) are effective when available.³