What is the optimal work-up for patient with repeatedly negative biopsies of a mid-rectal lesion with signs of malignant etiology?

It is not that rare to get negative biopsies initially in rectal cancer, as superficial tissue only is biopsied. I generally recommend that at repeat biopsies, attempts are made to biopsy deeply to get diagnostic tissue. One approach is to have the surgeons biopsy with a rigid endoscope- they can us...