# Molecular subtypes of breast cancer in Jamaican women: high prevalence of triple-negative and HER2 + disease

## TL;DR

This study finds that Jamaican women have high rates of aggressive breast cancer types, which may explain higher mortality and highlight the need for better treatment strategies.

## Contribution

The study provides the first comprehensive molecular characterization of breast cancer in a predominantly Black Caribbean population.

## Key findings

- Triple-negative breast cancer was found in 27% of Jamaican patients, a notably high prevalence.
- HER2-positive disease accounted for 25% of cases, indicating a significant proportion of aggressive tumors.
- Triple-negative tumors were associated with higher tumor grade and smaller tumor size.

## Abstract

Breast cancer incidence and mortality patterns vary significantly across populations, with women of African ancestry experiencing disproportionately higher mortality despite lower incidence rates. Jamaica reports concerning breast cancer mortality, yet comprehensive molecular characterization of breast cancer in this predominantly Black Caribbean population remains limited.

We conducted a retrospective cross-sectional study of 1312 female breast cancer patients diagnosed at the University Hospital of the West Indies in Jamaica between January 2012 and December 2016. Medical records were reviewed for patient demographics, tumour characteristics, and receptor status (estrogen receptor, progesterone receptor, and HER2). Tumours were classified into four molecular subtypes: HR + /HER2- (estrogen receptor positive and/or progesterone receptor positive, HER2 negative), HR + /HER2 + (estrogen receptor positive and/or progesterone receptor positive, HER2 positive), HR-/HER2 + (estrogen receptor negative and progesterone receptor negative, HER2 positive), and triple-negative (HR-/HER2-: estrogen receptor negative and/ progesterone receptor negative, HER2 negative). Bivariate analyses and logistic regression models assessed associations between clinicopathological features and molecular subtypes.

Mean age at diagnosis was 55.1 ± 13.6 years. The predominant tumour characteristics were invasive ductal histology (82%), SBR grade 2 (37%), and tumours ≤ 2 cm (31%). Molecular subtype distribution revealed HR + /HER2- (49%), HR + /HER2 + (13%), HR-/HER2 + (12%), and triple-negative (27%). Notably, total HER2 + disease accounted for 25% of cases. Triple-negative tumours were significantly associated higher grade (AOR = 13.92, p  < 0.001), and smaller tumours had reduced odds of being triple negative (AOR = 0.47, p < 0.05). Lobular carcinomas showed lower odds of being triple-negative (AOR = 0.17, p < 0.01) compared to ductal carcinomas.

Jamaican breast cancer patients exhibit a distinctive molecular profile with a high prevalence of both triple-negative (27%) and HER2 + (25%) disease, which likely contributes to poor outcomes in this population. These findings underscore the need for population-specific approaches to breast cancer management in Jamaica, including universal receptor testing and improved access to targeted therapies, particularly anti-HER2 agents.

The online version contains supplementary material available at 10.1186/s13058-025-02175-7.