The present invention relates to a method for assessing a cancerous state of a mammal-derived specimen, which comprises: (1) a first step of measuring a methylation frequency of Neurofilament3 gene contained in a mammal-derived specimen or an index value having the correlation therewith, and (2) a second step of determining a cancerous state of the specimen based on a difference obtained by comparing the measured methylation frequency or the index value having the correlation therewith, with a control; and the like.