Novel morphological study of solar lentigines by immunohistochemical and electron microscopic evaluation

Abstract

Solar lentigines (SL) are hyperpigmented lesions generally seen in elderly people. Their pathogenesis has not been completely elucidated. We examined 75 cases of SL using routine histopathology and immunohistochemistry. In addition, seven cases were evaluated by electron microscopy. Histopathologically, we observed vacuolar changes in the dermoepidermal junction in 85% of the cases. Dermal melanophages were seen in 77% of the cases. The immunohistochemical expression rates in the epidermis for cytokeratin (CK)15, CK14, CK10, p63 and nestin were 76%, 100%, 100%, 100% and 17%, respectively. In 58 cases showing dermal melanophages, expression rates of CD163 and factor XIIIa on melanophages were 79% and 83%, respectively. Double positivity for both proteins was identified in 44 cases (75%). Ultrastructurally, vacuolar structures were seen in the cytoplasm of basal cells and upper dermis in all cases examined. We observed elimination processes of damaged basal keratinocytes, which were probably produced by ultraviolet (UV) irradiation, into the papillary dermis. The segregated damaged cell bodies containing melanin granules seemed to be phagocytosed by poorly immunostimulatory macrophages labeled immunohistochemically by CD163 and factor X IIIa, contributing to prolonged pigmentation of SL. In addition, repeated basal keratinocyte damages may be in association with altered CK and p63 expression patterns in the constituent cells of SL.

Telomerase reverse transcriptase promoter mutations in primary cutaneous melanoma

“…Other features that supported the same proposition included association of the mutations in melanomas arising at the site of solar lentigines, the hyper pigmented lesions that are mostly seen in sun-damaged areas of skin 33 . BRAF mutations, in contrast, have been shown to be more prevalent on non-chronically exposed sites than the chronically exposed sites 31,32,34 .…”

Markers of health and disease and pigmented spots in a middle-aged population

“…Dear Editor , Pigmented cutaneous spots, such as actinic/solar lentigines, develop with advancing age and are most commonly observed in chronically sun‐exposed areas of the skin, such as the face, neck and dorsa of the hands . Actinic lentigines are characterized histopathologically by hyperpigmentation of the epidermal basal layer with an elongation of the epidermal rete ridges, and an increase in the number of dermal melanophages with deficient migration and digestive abilities …”

“…1 Actinic lentigines are characterized histopathologically by hyperpigmentation of the epidermal basal layer with an elongation of the epidermal rete ridges, 2 and an increase in the number of dermal melanophages with deficient migration and digestive abilities. 3,4 Other than cumulative ultraviolet (UV) exposure, risk factors for actinic lentigines are largely unknown. However, endocrine abnormalities, genetic factors, oestrogen levels, thyroid dysfunction and lower vitamin D levels have been identified as potential risk factors for some disorders of pigmentation (e.g.…”

“…10 These observations suggest that vitamin D might also play a role in hyperpigmentation, for example by suppressing the immune response to UV-induced epidermal damage leading to reduced clearance of aberrant melanin deposits. 3 Although the multivariate analysis was adjusted for sun-exposure behaviour, it is unclear whether 25-hydroxyvitamin D was just an additional proxy measure of sun exposure. IGF-1 on the other hand has previously been shown to delay the onset of UVBinduced apoptosis in keratinocytes.…”

Biological processes in solar lentigo: insights brought by experimental models

“…Numerous immunohistochemistry‐based studies using SL biopsies have qualitatively evaluated the presence of biomarkers specifically associated with different skin layers and involved in the pigmentation process .…”