Study of Fibroepithelial Lesions of Breast at a tertiary Care Centre- an Audit, Clinicopathological APPROACH and Comparison with WHO Grading

Background: Mammary fibroepithelial lesions cover a wide range of malignancies, from indolent fibroadenoma to the potentially fatal phyllodes tumor (PT). The morphological assessment criteria used for classification are typically difficult to apply, and there is no consensus on what constitutes a sufficient resection margin. The current study objectives were to investigate the histopathological spectrum of fibroepithelial lesions of the breast at a tertiary care centre, to stratify and classify various fibroepithelial lesions into fibroadenomas and PT, and to reclassify all confirmed cases of PT seen during the study period using standard histopathological WHO criteria. Methods: Between January 2016 and August 2019, records and slides of fibroepithelial lesions of the breast obtained at the department were retrieved and reviewed. Results: During this time, 891 fibroepithelial lesions of the breast were discovered. There were 826 (92.7%) cases of fibroadenoma and its variations, 34 (3.8%) cases of fibroadenomatoid mastopathy, and 31 (3.5%) cases of PT. Eight (25.8%) of all PT were borderline, four (12.9%) were malignant, and the remaining (61.3%) were benign. Conclusions: Fibroepithelial tumours of the breast are a diverse group of lesions that range in severity from benign fibroadenoma to malignant PT. Various subtypes have overlapping histologic characteristics, and transformation and progression to a more malignant phenotype are possible.  As there are significant clinical disparities among subtypes, precise pathologic categorization is critical for proper management. Despite the fact that some immunohistochemical markers may be helpful in this differential diagnosis, histomorphology is still the gold standard.