Answer

Multiple actinic keratoses - Bowenoid type.

Actinic keratosis is the most common epithelial precancerous lesion seen in more than 50% of the elderly, fair skinned individuals in hot sunny climates. ^[1] It presents as scaly, erythematous papules and plaques, usually few millimeters to less than 1 cm in diameter, on the sun-exposed areas. More than 80% of actinic keratoses occur on the upper limbs, head and neck area. ^[2] Actinic keratoses may remit or remain unchanged for many years. The risk of squamous cell carcinoma, if left untreated, varies from 8 to 24%.

Histopathology shows certain common features such as disturbed keratinocyte maturation, irregular and large keratinocyte nuclei, dyskeratotic keratinocytes, mitotic figures, solar elastotic changes in the upper dermis and variable inflammatory infiltrate. Apart from the above histopathological features, based on the presence of certain additional features, hypertrophic, atrophic, pigmented, acantholytic and bowenoid types of Actinic keratoses have been described. ^[3] The bowenoid type shows full thickness dysplasia of the epidermis.

Vitiligo is an acquired pigmentary disorder characterized by well-circumscribed depigmented macules and patches devoid of identifiable melanocytes. It affects both sexes and all races and its incidence in certain parts of India is as high as 1.13%. ^[4] The major function of melanin in humans is protection of lower layers of the skin against the ultraviolet rays (UVR). The damaging role of UV-light is well illustrated by the high incidence of epidermal carcinomas in Europeans exposed to tropical sun. ^[5] UVR may not be as significant an etiologic factor in the development of skin cancer in dark races because of the protection provided by melanin pigment against solar carcinogenesis. ^[6] Although the depigmented patches of vitiligo over the sun exposed areas such as the face, dorsa of the hands and forearms are prone to sunburn, the incidence of malignancy is rare. The rarity of skin cancer in patients with vitiligo may be due to the fact that these patients tend to avoid sun exposure. Though according to earlier observations skin cancer is rare in patients with vitiligo, there may be a small subset of patients with vitiligo who are at risk of developing various cutaneous malignancies such as those who received PUVA therapy. ^[7] Chronic sun damage per se could play a causative role in the development of actinic keratoses and squamous cell carcimonoma. ^[8] Hexel et al observed an increased or equal risk of nonmelanoma skin cancer in a cohort of 477 Caucasian patients with vitiligo. ^[9]

Since vitiligo is a frequently encountered condition, any persistent lesion over the sun exposed, depigmented area should be viewed with suspicion and needs to be biopsied to rule out in situ as well as invasive malignancies.