2.4. Interpretation of IHC Staining

Positive SLC34A2 IHC staining was detected in the membrane of tumor cells. SLC34A2 IHC expression was scored according to the percentage of positively stained tumor cells (0, <10%; 1, 10%–40%; 2, 40%–70%; and 3, >70%) and the intensity of staining (0, negative; 1, yellowish; 2, light brown; and 3, dark brown). A final immunoreactivity score was obtained for each case by multiplying the percentage of stained cells score by the intensity score (0–9) [5, 12, 13]. IHC analysis of SLC34A2 was blindly performed by 3 pathologists without any prior knowledge of the clinicopathological data. Any discrepancy between the 3 pathologists was resolved using a multihead microscope to reach a consensus.

Immunoreactivity for SLC34A2 was classified into 2 groups, namely, low expression (final score <  6) and high expression (final score ≥  6) [5].