We devised a color-imaging diagnosis for cancer, photodynamic histo-diagnosis (PDHD), with which we could clearly discriminate between cancer lesions and normal tissues. In an attempt to check the accuracy, we reexamined the PDHD method using two different types of colon tumors surgically harvested. The two specimens were treated according to our own procedures to microscopically observe reddish-pink fluorescence specifically emitted at cancer lesions. After which, such samples were modified to routine hematoxylin and eosin (HE) sections. Normal portion of the colon served as the control. To evaluate the diagnostic accuracy, we compared our PDHD findings with that of the HE sections. The two colonic samples emitted reddish-pink fluorescence by the PDHD method, which suggested that they were cancer lesions. While, diagnosis with the HE sections revealed one was "cancer in adenoma" and the other was "adenoma with no signs of cancer". This result suggested all was not cancer that emitted reddish fluorescence with our PDHD.