Tehran University of Medical Sciences Basic & Clinical Cancer Research 2228-6527 17 2 2026 10 10 54 62 Hussein Mahdi Kadhim College of Medicine, University of Kerbala, Karbala, Iraq BAHAA Aldeen HADI University of kerbala 2026 08 02 2026 09 02 BACKGROUND HER2 overexpression marks out a biologically aggressive targetable subset of breast cancer accounting for 15–20% of cases in Western series Data from Iraq are limited and Karbala Province has not been studied before MATERIALS AND METHODS We reviewed 99 women with confirmed invasive breast cancer at a single Karbala centre grouped into four age bands (28–39 40–49 50–59 60–69 years) HER2 was scored 0 1+ 2+ or 3+ by immunohistochemistry (IHC) using the 2013 ASCOCAP guideline We tested associations with age and histological type using chisquare tests and multivariable logistic regression (HER2 3+ as the dependent variable) reporting odds ratios (OR) and 95% confidence intervals (CI) RESULTS The 40–49year band was largest (333%) Invasive ductal carcinoma was the most common type (566%) followed by locally advanced disease (162%) invasive lobular carcinoma (121%) metastatic carcinoma (81%) and triplenegative breast cancer (71%) Fortyseven tumours (475%) were HER2negative (IHC 0); of the rest 13 (131%) scored 1+ 13 (131%) scored 2+ (equivocal) and 26 (263%) scored 3+ meeting strict ASCOCAP positivity criteria HER2 score was not linked to age (χ² = 782 p = 025) but histology varied significantly with age (χ² = 524 p < 0001) No variable independently predicted HER2 3+ positivity (IDC vs other: OR 175 95% CI 068–452 p = 024) CONCLUSIONS Over half of this cohort showed detectable HER2 expression and the strict HER2positivity rate (263%) is higher than the global benchmark in line with other Arab cohorts Reflex FISH was not available onsite to confirm equivocal (2+) cases pointing to a need for expanded confirmatory testing Histology but not age alone varied meaningfully across age groups which should inform diagnostic planning https://bccr.tums.ac.ir/index.php/bccrj/article/view/608