Abstract: It is intended to provide a method of assessing cancerous conditions, which is useful in diagnosing cancer in a therapy or a preventive therapy for cancer diseases or a maintenance therapy therefor, and a reagent for detecting a gene product to be used in the above method. The cancerous conditions of a human-origin specimen is assessed by using, as an indication, the content of a gene product, which shows an increase or a decrease in the expression thereof due to an unusual alternative splicing, from gene products obtained from human PTCH1 gene contained in the human-origin specimen.