A Case Series With Acquired Dermal Melanocytosis: A Retrospective Study From 2001 to 2018

Acquired dermal melanocytosis (ADM) is a pigmented lesion caused by melanocytes in the dermis, and it is most often observed on the face of young and middle-aged Asian women. ADM development may be associated with melanin synthesis alterations, but little evidence of its molecular and histological alteration has yet been reported. This study aimed to evaluate ADM in different body locations using different immunohistochemical and chemical staining techniques. This retrospective case series includes consecutive patients confirmed as ADM by biopsy between 2001 and 2018. Patient data and archival images were used to determine the pattern and duration of skin lesions, as confirmed by data analysis of immunohistopathological staining of skin biopsy specimens. A total of 22 ADM patients were included with mean age at diagnosis of 47 years, and 63.6% were female. The most common site was limbs (36.4%), followed by face (27.3%), trunk (22.7%), and scalp (13.6%). Melanin levels were highest in the face and upper extremities and lowest in the trunk. All participants had perivascular distribution of dermal melanocytes, particularly on the face and limbs. The perineural distribution of dermal melanocytes was observed in the lower limbs, with prominent inflammation and fibrosis on the scalp. Dermal melanocytes expressed most markers recognizing melanocytes except for CD117. Analysis of this ADM case series has confirmed that melanin is activated by dermal melanocytes that may aggregate along blood vessels. CD117 may be a useful biomarker by which to identify the migration of epidermal melanocytes.