Immunoexpression of Ki-67 Labelling Proliferation Index in Phyllodes Tumour of Breast by Polymer-based Detection Method

Abstract

Phylloides tumours (PTs) are rare breast neoplasms with a variable clinical course depending on the tumour category. The classification of PTs proposed by the World Health Organization (WHO) into benign, borderline and malignant is based on a combination of several histologic features, including Stromal cellularity, nuclear atypia, mitotic activity, stromal overgrowth and tumour margin appearance. However, there are no defined criteria or clear cut-offs for individual histologic parameters. Thus, the diagnosis of PTs based on the integration of morphology remains challenging. Along with the grade, additional study of proliferative markers such as Ki-67 are essential to identify those with potential for aggressive behaviour. This study was undertaken to assess the histopathological characters and correlate Ki-67 expression in different subtypes of PTs. In this study, 30 cases of PTs were studied. Regarding histologic features, routine H&E stains were taken into consideration for diagnosis and classification of tumours. Immunostaining for Ki-67 was also performed by polymer-based detection method. Ki-67 labelling index (LI) was categorized as 0-10, 11-30, 31-50, 51 and above depending on the percentage of positive tumor cells and was correlated with histologic grade and clinical features in each case. Twenty cases (66.7%) of benign phyllodes tumour (BPT), 3 cases (10%) of borderline PT, and 7 cases (23.3%) cases of malignant phylloides tumour (MPT) were examined in this study. Among 20 cases of BPT, 3 cases (15%) were recurrent tumours. Average Ki-67 LI in BPT was 5% (range 1-10%) and borderline PT was 17.5% (range 15-20%). MPT exhibited Ki-67 LI range of 15-35% with average LI of 25%. A significant association was seen between expression of Ki-67 in different grades of PT(p=0.01). So, Ki-67 LI should be performed in routine histopathology reporting of phylloides for sub-categorisation of phylloides.