Abstract:

A 36-year-old female presented with multiple dark brown papules on the chest and abdomen for more than 10 years, which had gradually increased in number. Physical examination revealed dozens of dark brown, flat papules measuring 1-3 mm in diameter in the chest and abdomen. Most of the lesions had a smooth surface, and some lesions gave a papilloma-like appearance, with no confluent trend. Biopsy of abdominal lesions showed mild hyperkeratosis of epidermis, acanthosis, extension of epidermal protrusions forming a reticulated appearance, horn pseudocysts in prickle cell layer, enhanced pigmentation of basal layer, and a sparse lymphocytic perivascular infiltrate in superficial dermis. A diagnosis of dermatosis papulosa nigra （DPN） was made.

Key words: differential diagnosis