Female malignant breast lesions: the Lagos University Teaching Hospital experience (1999–2013)

Abstract

Background: Breast cancer is the most common cancer in women worldwide and its incidence has been on the increase. Nigeria is no exception to this trend.

Objectives: The aim of this study is to review malignant breast lesions seen in the Lagos University Teaching Hospital over a 15yr period (1999-2013) with a view to determining the variety of histopathologic types seen, as well as to determine the molecular characteristics of a smaller cohort of these lesions with immunohistochemistry using a panel of 5 antibodies on tissue microarray.

Methods: The histopathology reports of breast lesions seen in the Anatomic and Molecular Pathology department of LUTH between 1999 and 2013 were retrieved, reviewed and analysed to determine the frequency of malignant breast lesions seen over the past 15yrs. Representative tumour slides and paraffin blocks of a smaller cohort of 115 consecutive cases seen in the last three years of the study were retrieved, reviewed and jointly scored by a Nigerian pathologist (AOD) and a UK specialist breast pathologist (AM) following the RCPath guidelines. Representative tumour areas were selected on the slides and marked on the corresponding paraffin block for tissue microarray (TMA) construction. TMA sections were stained for ER, PR, HER2, CK5 and E-cadherin.

Results: A total of 4450 breast biopsies were studied; 22.3% of these neoplasms were malignant; 97.9% of all malignant breast lesions were epithelial in origin. Invasive ductal carcinoma of no specific type (IDC, NST) was the predominant histologic type accounting for 86.6%. Ductal carcinoma in situ (DCIS) and lobular carcinoma were seen in 3.2% and 1.5% respectively. A mixed ductal and lobular pattern was seen in 1.4%. Mucoepidermoid carcinoma, carcinoid tumour, and papillary carcinoma were rarely recorded, accounting for 0.1%, 0.2% and 0.4% respectively. In the smaller cohort of 115 breast cancer cases with immunopheno typing carried out , immunohistochemical staining revealed 24.4% oestrogen receptor (ER) positivity, 13.9% progesterone receptor (PR) positivity and 5.2%, human epidermal growth factor receptor-2 (HER2) positivity (score of 3+), 4.3% were equivocal ( 2+). Thirty-five percent of tumours were triple negative breast cancers (TNBC)and 52.5% of these were CK5 positive suggesting a basaloid phenotype.

Conclusion: Malignant breast lesions, form about a quarter of all breast lesions seen in our laboratory, Majority (86.6%) are IDC, NST. A relatively high proportion (35%) of the immunophenotyped cohort consisted of TNBCs and about half of these had a basal phenotype (CK5+). More markers of the basal phenotype will be required to make a definitive statement on the proportion of TNBCs that have a basal phenotype.

Keywords: Breast cancer, histopathologic pattern, immunohistochemistry, basal phenotype