Abstract
High grade transformation （HGT） is an uncommon phenomenon among adenoid cystic carcinomas （AdCC） and is associated with increased tumor aggressiveness, with a high propensity for lymph node and distant metastasis. The patient was a 69-year-old woman with the chief complaint of swelling in the midpalate. At the first visit, a broad basal mass measuring 30×15mm was found slightly to the left of the center of the palate. As a result of the biopsy, it was diagnosed as a salivary gland malignant tumor, but a definitive diagnosis was not reached. Therefore, total resection was performed. By then, the tumor had significantly increased. A resected specimen showed that the tumor was composed of both a conventional low-grade AdCC and a HGT carcinoma. The part of the tumor that had increased rapidly from the first visit to the time of surgery was histopathologically occupied by HGT-AdCC. A positive margin was found in the histopathological specimen, and postoperative radiation was performed. Subsequent image evaluation revealed metastatic lung tumor and so concurrent chemoradiotherapy was performed, however, death resulted.
