The co-expression of estrogen receptor beta (ERß) and smooth muscle actin in phyllodes tumour of breast: A tissue microarray study

Proliferation of phyllodes tumour is mainly in the stromal that is considered as the neoplastic component of phyllodes tumour. Estrogen Receptor (ER) that plays an important role in breast neoplasm is also involved in progression of phyllodes tumour. ERβ is a type of ER which was reported to be expressed in the breast stroma while the expression of smooth muscle actin (SMA) in the stroma may differentiate histological grade of phyllodes tumour. We compared the expression of ERβ to SMA in stromal component of phyllodes tumour using tissue microarray (TMA) technique. A TMA was constructed on 77 cases of phyllodes tumour (46 benign, 17 boderline and 14 malignant) using 0.6 mm punch kit (Alphelys Plaisir, France) and immunohistochemical staining was done using ERβ and SMA. Phyllodes tumour seen in women aged more than 40 year-old with benign phyllodes tumour showed the lowest median of age (p=0.017). ERβ expression in stromal component increased with histological grade of the tumour. SMA was positive in 62.8, 41.2 and 57.1% of benign, borderline and malignant phyllodes tumour, respectively. Both ERβ (p=0.024) and SMA were commonly expressed in women aged ≥40 years. We found a significant co-expression of ERβ and SMA (p=0.047) and 65.5% of these cases occured in women aged more than 40 years-old. The high expression of SMA in stroma of benign phyllodes tumour may demonstrate the potential of proliferation of this tumour to become malignant. High expression of ERβ of malignant phyllodes tumour and its significant association with SMA suggests that co-expression of these two markers may play a role in stromal tumorigenesis of phyllodes tumour.