Melanin distribution in corneocytes and fine patterns of pigmentation on pigmented areas in pigmentary disorders

Background/aims: Hyperpigmentation on the face, such as chloasma, ephelides, and senile pigmentation, is a common problem in the dermatological field. It is desirable to obtain precise data on melanin distribution and hyperpigmentation patterns for correct diagnosis and suitable treatment; however, there are few reports of non‐invasive studies of hyperpigmentation of the face skin. Methods: In this study, we examined melanin distribution in corneocytes and fine patterns of pigmentation. Using adhesive tape, we stripped the skin on both pigmented areas and adjacent normal areas of the face. The melanin granules in the cells of the stripped specimens were stained by the Fontana‐Masson stain method. The melanin distribution of corneocytes was categorized into five types, and the frequency of each type was calculated. Pigmentation patterns were imaged by a videomicroscope equipped with a polarizer. The fine patterns of pigmentation were categorized into three basic patterns: reticulated, granulated and flat pigmentation. Results: Melanin granules were concentrated around the nuclei in pigmented areas compared with normal areas. The frequency of each fine pattern was different in each pigmented disease. Conclusions: This study will be useful in assisting dermatologists in correcting clinical diagnoses of pigmented skin diseases.