A low-grade dedifferentiated mucoepidermoid carcinoma of the retromolar trigone: A rare case report

Dedifferentiation is a rare phenomenon in mucoepidermoid carcinoma (MEC), and it has not been observed in the minor salivary glands. We describe the case of a 22-year-old woman with dedifferentiated MEC that originated in the retromolar glands. We performed tumor excision, and histopathological examination revealed dedifferentiated MEC based on FISH-based analysis of MAML2 gene rearrangement. The manner of dedifferentiation in our case was slightly different from that in MEC reported previously, and it was considered “low-grade” dedifferentiation. In 3.75 years since the surgery, the tumor has recurred locally twice, and in both cases, a good response to heavy-particle irradiation was achieved. The patient is still alive, and local control has been maintained.