| 摘 要： | ![]()
Hyper-pigmentation is a common, acquired dermatological skin-disorder manifesting and identifiable as irregular brown or greyish-brown facial discolouration, and sometimes referred to as melanosis, melasma or hypermelanosis. Purpose and Objective： To identify the site of melanin deposition in skin-layers regarding facial hyper-pigmentation, based on a histological study of full-thickness skin-facial biopsies in aged Caucasian-cadavers. Hypothesis： Recalcitrant hyper-pigmentation, is chiefly characterised by hyper-melanosis restricted to the dermal-layer of the integument. Method： The histological features of facial hyper-pigmentation and solar-lentigenes were evaluated in a pilot-study of 5-randomly selected Caucasian-cadavers with pigmentation （15 facial biopsies）, ranging in age between 75 and 102 years （mean 77-years）. Selection-criteria included, both genders, age 〉 75, focal and confluent hyper-pigmented lesions, involving sun-exposed areas of skin （centrifacial, scalp, malar, mandibular and cervical）. Study groups included （Grp-1： Control skin-histology in otherwise normal aged, human-cadavers; Grp-2： Histology of pigmented facial skin-lesions in man; Grp-3： Comparative histological skin-controls in non-human primates）. No obvious hepatic disease was evident in the cohort studied. Twenty-five histological controls were obtained from non-pigmented areas. Histological evaluation of full-thickness skin-biopsies （including the lesion, edge and peri-]esion skin）, was under a Leitz~-light-microscope, and staining included H＆E, Masson-trichrome, Masson-fontana, Alcian-blue and Verhoef technology. Histological-scoring used was on histological deposition of melanin in skin-layers： epidermal, dermal, mixed, and indeterminate melanin-deposition （score 1-4）. Controls included cadaveric skin-biopsies of human races of colour and non-human primate, Cercopethicus Aethiops （latter is known to have predominantly dermal-melanin deposition）. Pigmented and non-pigmented areas were compared in both species. Results： The majority of clinically visible individual and confluent areas of hyper-pigmentation studied were maeroscopically present on the forehead, frontal scalp in hair-receded cadavers, molar and temporal zones. Histologically, documented features of age-related changes without pigment were present in almost all the embalmed cadaver-skins, with a melanin-score of 1. Computer enhanced skin geometry and biometrics confirmed the presence of an aged-skin, pigmentation and features of solar damage. The human embalmed-tissue was well preserved and minimal autolytic changes were present. Special stains of full-thickness biopsies （Masson-Fontana）, showed that melanin in the subhuman-primate is lodged in the deep dermis （reticular dermis）, within the extra-cellular matrix （ECM） and superficial to the hypodermal adipose-tissue （melanin-score 3）. Fifteen pigmented lesions studied in five （5） aged-cadavers （forehead, molar and mandibular areas） all showed predominantly epidermal-deposition of melanin in the basal, suprabasal and stratum corneum with tiny focal areas of dermal melanosis in single-cell macrophages in the papillary-dermis but not reticular-dermis （melanin-score 2）. A melanin-deposition localization ratio of epidermis to dermis was approximately 98 to 2% in cadavers with hyper-pigmentation. Conclusion： The skin-strata localization of the melanin with regards hyper-pigmentation of the face and forehead in this aged, human adult Caucasian, cadaveric-study, was predominantly in the epidermis and sparse in the papillary dermis.
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