卡波西氏肉瘤是後天免疫不全症候群（AIDS，愛滋病）最常見的惡性腫瘤，但是並不是所有的卡波西氏肉瘤都有後天免疫不全症候群。我們報告了一例卡波西氏肉瘤，但是愛滋病病毒感染陰性的病患。因為病患之前同一位置經過了兩次切除仍然復發。經過討論之後，在第三次手術切除之後，追加放射線治療以增加局部控制。我們使用了5040 cGy的放射線治療，兩年的追蹤並沒有腫瘤的復發。根據我們的經驗及文獻回顧，局部的卡波西氏肉瘤對放射線照射是相當敏感且有效的。

Kaposi's sarcoma (KS) is the most common malignancy associated with the acquired immunodeficiency syndrome (AIDS). However, not every patient with KS has AIDS. The classic form of KS is a rare disease. We present a 50-year-old Taiwanese with KS who was seronegative for human immunodeficiency virus (HIV). Because the tumor recurred twice after surgery, we used radiotherapy as the adjuvant therapy after the third surgical procedure yielded a specimen with unclear margins. The patient received a total of 5040 cGy in 28 fractions with a special designed water bolus. There was no evidence of recurrence 24 months later. According to the literature and our experience, radiotherapy is useful for localized KS.