PURPOSE:Colonoscopy with biopsy(ies) is performed in patients with colorectal cancer for diagnosis and screening of synchronous lesions. There is some fear of spreading the disease related to implantation of tumor cells at sites of mucosal damage or to hematogenous or lymphatic spread as a result of tumor manipulation.METHODS:A total colonoscopy including biopsies, performed in a patient because of anal blood loss and tenesmus, revealed a circular, polypoid, ulcerated mass from 1.5 to 12 cm above the anal verge. After preoperative radiotherapy, the patient was subjected to surgical intervention.RESULTS:Histopathology revealed a poorly differentiated rectum adenocarcinoma, staged pT4N1Mx. At approximately 12 cm proximally from the tumor, a biopsy taken through a minute irregularity of the mucosa revealed some granulation tissue with adjacent normal colon mucosa. The basis of this granulation tissue, corresponding to submucosa, contained poorly differentiated tumor elements.CONCLUSIONS:This tiny lesion might have been caused by implantation of exfoliated cancer cells in a biopsy site. It may not be without risk to create excessive biopsy lesions in the presence of a manifestly malignant tumor because of the possibility of tumor cell implantation.