PGR and triple-negative breast carcinoma: Triple-negative breast cancers (TNBC), a special class of breast cancers that are negative for oestrogen receptor (ER), progesterone receptor (PR) and HER2 (cerbB2), represent 9–17% of all breast carcinomas, depending on the threshold for ER, PR and HER2 positivity [1,3,4,5].