Urocanic Acid in Benign and Malignant Human Epidermal Tumors<xref ref-type="fn" rid="FN2">2</xref>

The presence of high histidine deaminase activity and the absence of urocanase resulted in the accumulation of urocanic acid in the epidermis. Benign epidermal tumors such as seborrheic keratoses and warts contained normal amounts of urocanic acid, whereas basal and squamous cell carcinomas had none or only trace quantities. This abnormality in malignant lesions is associated with normal amounts of histidine but an absence of histidase or urocanase. A Chromatographic method has been proposed for the rapid screening of epidermal tumors.