The DCC Protein and Colon Cancer

To the Editor: In their study of immunohistochemical staining of the DCC protein and its association with the prognosis of colorectal cancer (Dec. 5 issue), 1 Shibata et al. report that the absence of stainable DCC is predictive of mortality. Absence of evidence, however, is not evidence of absence. The authors used tissues that were paraffin-embedded, a method of preparation that may extract stainable moieties from cells and thus result in false negative results. Inasmuch as the authors found it necessary to employ a harsh protocol, involving microwaving cells under pressure, to enhance the performance of their staining procedure, one wonders . . .