5-Fluorouracil（5-FU）是廣泛的癌症治療藥物之一，使用後造成的皮膚相關症狀包括禿髮、皮膚炎、手足症候群（又名肢端紅腫）、光敏感。然而有少數的病例會誘發靜脈色素沉著，在皮膚上呈現蛇紋狀分佈，故稱為蛇紋狀色素沉著，屬於良性且可自癒的不良反應。這種現象也曾在使用其它化學治療藥物的病人身上被發現。本文將討論一位57歲直腸結腸癌患者使用5-FU治療後出現蛇紋狀色素沉著的案例。

5-Fluorouracil（5-FU）is one of the most widely used drugs for cancer. The common dermatological adverse drug reactions of this drug include alopecia, dermatitis, hand-foot syndrome (acral erythema), and photosensitivity. However, at times it could induce pigmentation of the skin overlying the venous network, like serpentine appearance as to be called serpentine hyperpigmentation. It is benign and self-limiting. Subsequently, this phenomenon has been observed in individuals treated with other chemotherapeutic agents. This report discusses a 57-year-old man with colorectal cancer who developed serpentine hyperpigmentation after being treated with intravenous 5-fluorouracil.