Cyclin D1 and p16 expression in pleomorphic adenoma and carcinoma ex pleomorphic adenoma of the parotid gland

Aims: To compare cyclin D1 and p16ink4 (p16) expression in normal tissue, pleomorphic adenoma (PA) and carcinoma ex pleomorphic adenoma (CXPA) of the parotid gland. Methods and results: Immunohistochemistry was used to examine cyclin D1 and p16 expression in 43 parotid tumours (29 PAs and 14 CXPAs). Cyclin D1 and p16 were both significantly more likely to be expressed in the neoplastic than in the normal epithelial and stromal components of PA and CXPA (P < 0.001 and P < 0.005, respectively). Cyclin D1 was more likely to be expressed in the malignant components of CXPA than in the benign components of PA (50% versus 31% and 31%, respectively), but the trend was not statistically significant. There was no evidence of this association for p16 (corresponding positivity rates 69% versus 81% and 52%). Conclusions: Our findings provide preliminary evidence of roles for cyclin D1 and p16 in the development of PA and for cyclin D1 in the progression of PA to CXPA.