Three histological sections from the initial biopsy: No 1 (left) — Well-circumscribed cystic lesion located within the bone. H&E, original magnification × 20. No 2 (center) — Initial biopsy showing a well-differentiated invasive squamous cell carcinoma with a lobulated architecture. H&E, original magnification × 40. No 3 (right) — Same cystic lesion squamous epithelium transitioning from a normal appearance (left) to carcinoma in situ and then to invasive carcinoma with stromal invasion. H&E, original magnification × 200.