**4.2. Calpain-1 expression in TNBC tissues**

Immunostained tissues with calpain-1 were significantly expressed and demonstrated cytoplasmic and membranous staining with some granularity and heterogeneity between adjacent tumor cells varying from weak to intense staining in which low staining was detected in 32.7% (18 of 55), intermediate staining in 38.2% (21 of 55) and high staining in 29.6% (16 of 55) of the cases analyzed. The cut off value was determined by screening the stained tissue under light microscope where the staining intensity of calpain-1 in tumor cells was assessed as none (0), weak (1), medium (2), and strong (3) using an immunohistochemical *H*-score. The *H*-scores were calculated by multiplying the percentage area by the intensity grade (*H*-score range 0–300).
