Radiation lentigo. A distinct cutaneous lesion after accidental radiation exposure.

BACKGROUND: Accidental exposure of skin to ionizing radiation leads to long-term alterations such as fibrosis, keratosis, and teleangiectasias. Also, noncharacteristic hyperpigmentation and hypopigmentation may be noted.

OBSERVATIONS: A distinct lesion is described on the calves of a white male survivor of the 1986 nuclear accident at Chernobyl, Ukraine. Several years after the accident at Chernobyl, characteristic pigmented macules developed in the areas of skin that had previously been exposed to ionizing radiation: there was a marked, sharply demarcated lentiginous hyperpigmentation of epidermal and basal keratinocytes and melanocytes, as well as an increase in the number of melanocytes. No cellular atypia was noted.

CONCLUSIONS: This case demonstrates the potential of high single doses of ionizing radiation to induce pigmented lesions with similar clinical and histological features as they have been described after exposure to natural UV radiation or radiation from a tanning bed or sunlamp or after therapy with oral psoralen with long-wave UV-A radiation (PUVA), described as solar, tanning bed, and PUVA lentigines. The absence of cellular atypia may account for a favorable prognosis and enables clear distinction from more serious diagnoses such as lentigo maligna melanoma.