Immunohistochemical breast cancer subtypes in Palestinian Women: an 18-year multicenter retrospective analysis

Abstract Objective To describe the demographic, geographic, and immunohistochemical (IHC) subtype distribution of breast cancer in a large multi-center Palestinian cohort, and to examine temporal trends in subtype frequency over an 18-year period. Methods A retrospective descriptive analysis of 2,323 consecutive female breast cancer patients diagnosed at 27 pathology service centers across 11 Palestinian governorates between August 2008 and May 2026. Estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor 2 (HER2), and Ki-67 status were abstracted from the immunohistochemistry reports. Patients with complete ER, PR, and HER2 data were classified into four molecular surrogate subtypes: Luminal A-like (HR+/HER2−), Luminal B HER2+ (HR+/HER2+), HER2-enriched (HR−/HER2+), and triple-negative (HR−/HER2−). Results The cohort was geographically broad, with the highest proportions of specimens contributed from Nablus (51.5%) and Ramallah & Al-Bireh (20.9%) governorates. Mean age at diagnosis was 52.8 years (SD 13.2; range 19–98). Among patients with reported IHC results, ER positivity was 67.4% (1,352/2,005), PR positivity was 63.4% (1,166/1,840), and HER2 positivity was 21.4% (425/1,985). Of the 1,628 patients with complete triple-marker data, Luminal A-like tumors comprised the majority (60.7%, n = 988), followed by triple-negative (17.6%, n = 286), Luminal B HER2+ (11.9%, n = 193), and HER2-enriched (9.9%, n = 161). HER2-enriched tumors occurred in younger patients (mean age 48.8 years) than the other subtypes. Conclusion Palestinian breast cancer is dominated by hormone-receptor-positive disease, but the combined HER2-positive fraction (21.8%) and triple-negative fraction (17.6%) together account for nearly two-fifths of cases — a higher burden of aggressive subtypes than is reported in most Western series. These findings underline the importance of universal IHC testing and targeted therapy access in Palestinian breast cancer care.