To the Editor: Bowen disease (BD) is a squamous cell carcinoma in situ that can progress into invasive carcinoma.[1] Pigmented BD is a rare variant of squamous cell carcinoma in situ that can be diagnosed pathologically. It is usually characterized by slow-growing, well-defined, and non-uniform hyperpigmented plaque.[2] It is also characterized by the increased melanin pigment in the epidermis or papillary dermis in addition to the alteration of BD. In a study, 7 (1.67%) of 420 BD cases were pigmented.[1] Although the exact underlying mechanism of pigmented BD is unclear, pigmentation is due to the presence of an increased number of melanocytic hyperplasia by hypertrophic dendritic processes dispersed through the tumor.[3] Pigmented BD with no scaling and keratosis indicates well-differentiated stages of atypical keratinocytes developing melanin.[3] Later atypical keratinocytes result in loss of pigmentation, keratosis, and scaling. Herein, we present a rare case of pigmented BD on the proximal nail fold.
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