Fig. 4

Typical and variant patterns of intact mismatch repair protein expression. Some variation of staining is allowed as shown and the internal control is the key to proper evaluation. a Typical staining (MSH6): tumor (lower half image) showing similar staining intensity as background control/normal crypts (upper half image). b Expression in the tumor (MSH2, arrowheads) is stronger than background internal control (arrows). c Intratumoral patchiness/uneven staining (MSH6). Original magnification 400×