Supplementary Material for: Hidden Beneath the Nail Plate: A Case Report of Subungual Squamous Cell Carcinoma Mimicking Benign Nail Dystrophy

Subungual squamous cell carcinoma (SCC) is a rare malignancy often misdiagnosed due to its clinical resemblance to benign nail conditions. A 26-year-old male neurosurgeon presented with a four-year history of isolated nail changes, including longitudinal erythronychia and distal splitting of the left fourth fingernail. Despite the absence of pain or mass, his occupational exposure to ionizing radiation and active tobacco use raised suspicion. Dermoscopy was inconclusive, and imaging ruled out bone involvement. Histopathological evaluation of the excised nail unit confirmed SCC in situ. The patient underwent complete nail unit excision with periosteal dissection, followed by flap reconstruction. At four-month follow-up, he showed no signs of recurrence. This case underscores the need for early biopsy in persistent nail alterations, even among young patients, particularly when risk factors such as radiation exposure exist. Prompt histologic diagnosis allowed for timely, function-preserving surgical intervention.