A case of recurrent skin tumor with difficult differential diagnosis between keratoacanthoma and squamous cell carcinoma

A 92-year-old woman developed a small tumor on her cheek 3 months ago. Former dermatologists excised this tumor 3 times as keratoacanthoma, but the tumor reappeared 2-3 months after each operation. Pathological diagnosis was keratoacanthoma at the initial and second excisions, and squamous cell carcinoma at the third.The tumor was not excised completely at every operation under histological examination. At the fourth operation, the tumor size was 7×8mm at the skin surface accompanied with subcutaneous induration of 3×2×2cm. Wide excision and skin grafting were performed. Histologically, the tumor grew deep close to the cheek bone. Then radiation therapy was added after the operation. No local recurrence and metastasis was seen under the follow-up period of 3.5 years. [Skin Cancer (Japan) 2003; 18: 36-40]