It is to provide a tumor diagnostic agent and a tumor determination method enabling not only determination of the presence or absence of a tumor in a subject, but also determination of whether the tumor is a malignant tumor or a benign tumor, which can be used simply at low cost with reduced side effects and burden. 5-aminolevulinic acid (ALA) or its derivative, or a salt thereof is orally administered at a dose of 5 to 7 mg in terms of ALA per kg of body weight, and a urine sample 4 to 12 hours after the administration is collected. Porphyrins and creatinine in the urine sample are quantitated, and based on the value (nmol/gCre) obtained by dividing the amount of porphyrins by the amount of creatinine, a distinction among an individual without a tumor, an individual with a benign tumor, and an individual with a malignant tumor is determined. The presence or absence of a malignant tumor in a subject can be clearly determined by administering 1 to 3 mg of ALAs in terms of ALA per kg of body weight.本發明提供不僅可針對受檢者之腫瘤有無進行判定,亦可判別該腫瘤是為惡性腫瘤抑或良性腫瘤而為簡便且副作用或負擔較少且為低成本之腫瘤診斷劑及判定方法。該判定方法為將5-胺基乙醯丙酸(5-aminolevulinic acid)(ALA)或其衍生物或該等之鹽以ALA換算每1kg體重經口投與5~7mg,於投與4~12小時後採取尿試料。對於尿試料中之卟啉類及肌酸(creatine)進行定量,藉由將卟啉類量除以肌酸量之值(nmol/gCre)而判定未具有腫瘤者及具有良性腫瘤者與具有惡性腫瘤者之區別。以ALA換算對每1kg體重投與1~3mg之ALA類時,可明確判定受檢者有無惡性腫瘤。
