CLDN1 and neoplasm: In the present study, 45 IBC-NST and 46 IMPC samples (36 IBC-NST, 37 IMPCs and 9 mixed IMPC/IBC-NST cases with 91 tumor samples) were evaluated for claudin-1, -3, -4, and -7 immunohistochemical expression in search for the possible role of these markers in the formation of inverted polarity, in differentiating between IBC-NST and IMPC subtypes and as potential prognostic indicators.