Invasive breast carcinomas in Ghana: high frequency of high grade, basal-like histology and high EZH2 expression

Abstract

Breast cancer in African-American women has a worse outcome than in Caucasian women. The ancestors of most African-American women come from West Africa, including Ghana. The Polycomb group protein EZH2 is a marker of poor outcome in breast cancers from Caucasian women. The histopathological features and biomarker expression of African breast cancers remain obscure. Here, we investigated a cohort of Ghanaian breast cancers to better define the prevalent tumor types and to test if EZH2 protein may identify aggressive tumors. A group of 169 breast tissues (100 invasive carcinomas and 69 benign) from women treated at Komfo Anoyke Teaching Hospital between 2006 and 2011 were histologically classified and investigated for EZH2 expression. EZH2 nuclear expression we defined as high or low following previously published criteria. Of the 100 invasive carcinomas, 89 % were ductal, 2 % were lobular, and 9 % were metaplastic. Basal-like pathological features were present in 30 % of the tumors. Of the invasive carcinomas, 7 % were grade 1, 41 % grade 2, and 52 % grade 3. EZH2 protein was overexpressed in invasive carcinomas compared to benign breast (p < 0.0001). In invasive carcinomas nuclear EZH2 overexpression was significantly associated with basal-like subtype (p = 0.03) and high histologic grade (p < 0.05). Cytoplasmic EZH2, which has not been previously reported, was present in 16 % of invasive carcinomas and it was associated with triple negative status (p = 0.02). Our results provide the first comprehensive histopathological study of this patient population and uncover the association of EZH2 with high grade and basal-like tumors. We provide the basis for further detailed investigations on this cohort to advance diagnosis and treatment of African and African-American women.

Fig. 1

Histopathological features of Ghanaian invasive carcinomas. a and b Invasive carcinoma with high Nottingham grade, and basal-like features including syncytial growth pattern and central geographic necrosis. c Focus of squamous differentiation in a Ghanaian invasive carcinoma. d Metaplastic carcinoma with chondroid differentiation

Fig. 2

EZH2 protein expression in benign tissue and in invasive carcinomas from Ghana. a Fibroadenoma showing occasional epithelial cells expressing low nuclear EZH2. b A basal-like carcinoma with high EZH2 nuclear expression. The inflammatory cells mixed in with the tumor cells are negative for EZH2. Also note the EZH2 localization to the mitotic figures, consistent with a reported role of EZH2 in mitosis [17, 21]. c Representative picture of an invasive carcinoma with cytoplasmic EZH2 expression. The nuclei of the cancer cells are negative for EZH2. This pattern of EZH2 expression has not been described