En face histopathologic technic for examining colonic mucosa of resection specimens

The en face histopathologic technic for examining colonic mucosa in the plane of the luminal surface is described and analyzed. Grossly normal colonic mucosa from 56 resection specimens was embedded en face and sectioned. The en face histopathologic slides showed sheets of mucosa with the crypts in cross section surrounded by lamina propria, an orientation to mucosal topography analogous to gross examination. A total of 1,931 cm² of mucosa was embedded en face in 640 paraffin blocks, a mean of 3.0 ± 0.8 (SD) cm² per block. With routine processing of the same surface area, approximately 2,365 blocks (nearly four times as many as for the en face technic) would have been required. A total of 1,217 cm² of mucosa appeared in the slides from the en face blocks, comprising 63 ± 23% of the submitted tissue, compared with 0.3% in routine sections. Our analysis demonstrated that the en face technic is a useful tool in histopathologic studies of large areas of grossly normal colonic mucosa, particularly for quantitation and mapping of the findings.