Letter to Editor Subungual pigmented squamous cell carcinoma presenting as longitudinal melanonychia: a case report with review of the literature

Occurrence of squamous cell carcinoma (SCC) in the nail is rare [1], although it is the most common epithelial malignancy of the nail apparatus [1, 2]. Less than 300 cases of subungual SCC (invasive or in situ) have been reported in the English-language literature [2]. The clinical diagnosis of this type of tumor may be difficult and is often missed and/or delayed because of the heterogeneity of the clinical signs [1, 2]. Retrospective analyses of subungual SCC revealed that the clinical signs included subungual hyperkeratosis, leukonychia, erythronychia, and onycholysis, and it is often clinically diagnosed as verruca or onychomycosis [1, 2]. Approximately 10% of subungual SCC cases showed longitudinal melanonychia [1, 2], and a few cases of pigmented SCC in situ (Bowen’s disease) of the nail have been reported, among which some of them resembled malignant melanoma clinically [3-6]. However, the histopathological mechanism by which subungual SCC presents as melanonychia, such as the presence of melanocytes within the lesion, have not been evaluated yet. Herein, we report a case of subungual pigmented SCC presenting as longitudinal melanonychia with concise histopathological analysis and review of the literature.