ABSTRACT
Cutaneous squamous cell carcinoma is the second most common tumor in humans, and its incidence is increasing. In cutaneous squamous cell carcinoma, lymph node and distant metastases are rare, and bone invasion in the lower limbs is uncommon. A 67-year-old male presented with a solitary erythematous plaque on the fifth toe, accompanied by swelling. A shave biopsy was performed. The diagnosis of bone-invaded squamous cell carcinoma with aggressive behavior was made by combining the histopathological, immunohistochemical staining, and magnetic resonance imaging results. Mohs micrographic surgery was performed to remove the skin lesion and tumor-invaded bone. However, 2 months later, squamous cell carcinoma relapsed in the same area. After confirming the absence of lymph node metastasis, additional treatment, including ray amputation, was performed. Adjuvant radiotherapy was not administered. We present a rare case of squamous cell carcinoma that relapsed after Mohs surgery and was subsequently treated with ray amputation.