Fig. 2

Decision tree for the 3-tier interpretation of the CK7/SATB2 combination: If CK7 is absent, a lower gastrointestinal (LGI) primary (red bar) is most likely regardless of the staining pattern of SATB2. If CK7 is focal and SATB2 is diffuse, a lower gastrointestinal primary should be favored. The combination of focal CK7 and absent/focal SATB2 suffers from low numbers and second line markers should be considered. If CK7 is diffuse and SATB2 is absent or focal, this represents an ovarian (OV) primary (blue bar) with 96% probability. However, if both CK7 and SATB2 are diffuse, this scenario more likely represents a lower gastrointestinal primary