PROBLEM TO BE SOLVED: To provide a composition for diagnosing and/or treating cancerous pathologies in the field of urology. ;SOLUTION: The invention relates to a 5-aminolevulinic acid ester (E-ALA) solution for producing a pharmaceutical preparation useful for diagnosing and/or treating tissue pathologies and/or cell pathologies by local radiation exposure using radiation emitted by a light source energy followed, in the case diagnosis, by detection of fluorescent protoporphyrin IX (PpIX). The E-ALA concentration (c) in the solution is less than 1% and ranges between 0.01 to 0.5%. The low E-ALA concentration in the solution increases the synthesis of PpIX and homogenizes its distribution in the cell layers while highly reducing the secondary toxicity for the treated cells. ;COPYRIGHT: (C)2010,JPO&INPIT