As noted above, rectal tumors must be accurately local­ized prior to initiation of neoadjuvant treatment since assessment of distal resection margins after treatment is often difcult due to downstaging of the tumor. A few cave­ats should be mentioned. Tattooing with India ink for rectal cancer has been found by some investigators to be inaccu­rate with error rates ranging from 2% to 21% [19]. It should be remembered that submucosal tattoos that are placed pre­operatively are often difcult to visualize from the abdo­men because of the thick mesorectum. Some authors have suggested that submucosal rectal wall tattoos be placed in the operating room at the time of resection to accurately mark the distal resection margin [20], although this may not be possible in the setting of complete clinical response, which is why placement of tattoo at the time of diagnosis is favored. Unlike for intraperitoneal colon cancers, tattoo of extraperitoneal rectal cancers will primarily be visible dur­ing intraoperative endoscopy, and a exible colonoscope/ sigmoidoscope or rigid proctoscope should be available for localization during resection. Several case reports have also raised the issue of potential tumor implantation by improper endoscopic tattooing directly through the tumor, which obviously should be avoided [21]. In addition, tattooing may induce altered appearance of the rectal wall on MR or reactive lymphadenopathy, with possible resultant over­staging on MRI [22]. Thus, if a rectal tumor was not tat­tooed at diagnosis, it is optimal to obtain staging MRI and CT prior to marking the tumor endoscopically with ink. If