The following formula that fluoresce specifically in cancer tissue in a short period of time (I) (R 1 is hydrogen atom or a substituent When you apply to the site the presence of cancerous tissue is suspected hydrogen atom, a hydroxyl group is R 2 ~R 7 , a halogen atom or an alkyl group cancer diagnostic agent comprising, as an active ingredient a compound represented by) shows the C 1 -C 3 alkylene group X R 9 and R 8 is a hydrogen atom or an alkyl group.がん組織の存在が疑われる部位に適用すると短時間にがん組織において特異的に蛍光を発する下記式(I)(R1は水素原子又は置換基;R2~R7は水素原子、水酸基、アルキル基、又はハロゲン原子;R8及びR9は水素原子又はアルキル基を示し;XはC1-C3アルキレン基を示す)で表される化合物を有効成分として含むがん診断薬。
