The significance of enhancer of zeste homolog 2 (EZH2) expression in spindle cell lesions of the breast

Spindle cell lesions of the breast are rare entities and pose a diagnostic challenge for pathologists due to overlapping morphologic and immunohistochemical features. We evaluated EZH2 expression in various benign (fibromatosis (n = 8), myofibroblastoma (n = 7), neurofibroma (n = 1), nodular fasciitis (n = 5), benign phyllodes tumor (n = 18)) and malignant (malignant phyllodes tumor (n = 8), metaplastic breast carcinoma (n = 16) and angiosarcoma (n = 8)) spindle cell lesions as a potential diagnostic and therapeutic marker. The EZH2 expression was evaluated semi-quantitatively to categorize the cases as ‘low’ and ‘high’ expression. All benign lesions showed low EZH2 expression, whereas high EZH2 expression was observed in the majority (28/32; 88%) of malignant lesions. The study results suggest that EZH2 may be used both as an additional diagnostic tool to reach an accurate diagnosis of the spindle cell lesions of the breast and as a therapeutic target for the malignant lesions.