PCNA and adenoid cystic carcinoma: Ki-67, p53, bcl-2, epidermal growth factor receptor (EGFR), human epidermal growth receptor-2 (HER2), proliferating cell nuclear antigen (PCNA), and Runt-related transcription factor-3 (RNUX3) are representative markers of adenoid cystic carcinoma [4-6].