[OA-29] Histopathological characteristics of phyllodes tumour and cellolar fibroadenoma in core needle biopsy specimens in Army Institute of Pathology

Supasin Boocha and Kittisak Wongchansom

Division of Anatomical Pathology, Army Institute of Pathology, Bangkok, Thailand

Fibroepithelial lesions of the breast encompass various groups of tumours, including fibroadenoma and phyllodes tumour. Fibroadenoma can be clinically observed or complete excision with low recurrent rate, while phyllodes tumour needs wide local excision with negative margins. The diagnosis requires core biopsy assessment which is challenging especially between cellolar fibroadenoma and phyllodes tumour. The objective of this study was to differentiate histopathological features of phyllodes tumour and cellolar fibroadenoma on core needle biopsy. The cellolar fibroadenoma (n = 12) and phyllodes tumour (n = 24) slides from core needle biopsy and subsequent excision in army institute of pathology had been assessed. Histopathological features, including mitosis, stromal cellolarity, stromal overgrowth, nuclear pleomorphism, tumour heterogeneity, stromal fragmentation, fat trapping and subepithelial condensation, were evaluated on core needle biopsy slides. Twenty-four cases (66.7%) were diagnosed as phyllodes tumours. Twelve cases (33.3%) were diagnosed as cellolar fibroadenoma. The following three histopathological features were statistically significant differences among the two groups, i.e. mitosis, stromal cellolarity and subepithelial condensation. In conclusion, subepithelial condensation, stromal cellolarity (moderate or more) and mitosis (more than 1 per 10 HPF) are the most helpfol features to distinguish phyllodes tumour from cellolar fibroadenoma on core needle biopsy.

Keywords: cellolar fibroadenoma; core needle biopsy; fibroepithelial lesions; phyllodes tumour