A rare case of myoepithelial carcinoma gradually changing into malignancy: A report and literature review

A myoepithelial carcinoma (MC) is a very rare, low-grade tumor. Our patient was a 78-year-old female who presented with an indolent tumor on the hard palate's right side. We performed two biopsies at an 18-month interval and a complete resection and diagnosed it as predominant clear cell-type MC. Immunostaining revealed a greater proportion of cells positive for Ki-67 (MIB1) in the second biopsy specimen compared to the first biopsy specimen. These findings suggested that the tumor did not develop de novo in the tissues; rather, a benign tumor derived from myoepithelioma gradually changed into a malignant tumor over time.