Triple-negative breast cancer at Helen Joseph Hospital: Prevalence, age and imaging features.

Background: Triple-negative breast cancer (TNBC) is considered an aggressive subtype, defined by the absence of oestrogen, progesterone and HER2 receptors. It typically presents earlier and more aggressively. Limited data exist on its prevalence, age of onset and imaging features in South Africa. Objectives: This study aimed to assess the prevalence of TNBC at Helen Joseph Tertiary Hospital (HJTH), describe its histopathological features and explore trends in age at diagnosis and imaging patterns-including early-onset disease. Method: A retrospective review of 280 female patients with histologically confirmed breast cancer, diagnosed between January 2021 and December 2023, was conducted. Demographic, imaging and histopathology data were analysed using descriptive statistics and chi-square tests. Results: The diagnosis of TNBC accounted for 17% (48/280) of all breast cancer cases in the cohort. The TNBC lesions typically measured 1-5 cm and showed nodal involvement in 73% of cases. Despite their aggressive biology, many TNBC lesions appeared circumscribed or only mildly irregular on imaging, mimicking benign masses. Among all the 280 breast cancer cases, 61% were high-grade. The mean Ki-67 index for TNBC was the highest at 52%, followed by HER2+ (39%), Luminal B (33%) and Luminal A (21%). Notably, some HER2+ and TNBC cases exhibited lower Ki-67 indices, highlighting heterogeneity within these subtypes. Conclusion: This study highlights the complexity of breast cancer presentation in a South African setting, particularly the discordance between tumour biology and imaging. Contribution: These findings contribute local data on TNBC in an urban public healthcare context, supporting improved imaging awareness and clinical vigilance in resource-limited settings.