Formation of bone-like tissue in a giant adenocarcinoma (NOS) caused by radiation therapy in combination with retinoic acid

We report a case of a giant adenocarcinoma, not otherwise specified (NOS) with bone-like tissue formation that arose in the right cheek following radiation therapy in combination with retinoic acid after vascular embolization.A 74-year-old man was referred to our department because of a fist-size tumor in the right cheek. Biopsy of the tumor showed characteristic features of adenocarcinoma (NOS). Because the patient had massive bleeding from the oral tumor on an operation to create a percutaneous endoscopic gastrostomy, vascular embolization of the right external carotid, facial, and lingual arteries, which were feeding arteries of the tumor, was performed.For palliative treatment, he underwent chemoradiation therapy in combination with retinoic acid therapy. At the completion of primary therapy, there was no distinct change in tumor size. However, 8 months after treatment computed tomographic scanning revealed, tumor regression, as well as the appearance of numerous radiopaque masses, suggesting bone formation in the tumor tissue.