Introduction: Monodactylous longitudinal melanonychia (LM) may represent both benign and malignant dermatologic disorders. However, squamous cell carcinoma in situ (SCCis) is not commonly considered in this setting.
Case presentation: In this report, we present 2 cases of SCCis of the nail matrix in patients with skin of color who presented with monodactylous LM involving the lateral aspect of the nail.
Conclusion: These cases suggest that SCCis should be included in the differential diagnosis for monodactylous LM, especially when involving the lateral nail plate in darker skin.
Keywords: Bowen's disease; Melanonychia; Nail pathology; Squamous cell carcinoma.
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