Dedifferentiated adenoid cystic carcinoma of the trachea: a case report with respect to the immunohistochemical analyses of mammalian target of rapamycin pathway proteins

Dedifferentiated adenoid cystic carcinoma is an extremely rare and highly aggressive tumor. We describe the first reported case of dedifferentiated adenoid cystic carcinoma of the trachea and analyze the expression profiles of mammalian target of rapamycin pathway proteins. A 66-year-old Japanese man was incidentally found to have stenosis of the trachea, and a bronchial biopsy revealed low-grade adenoid cystic carcinoma. The resected specimen revealed dedifferentiated adenoid cystic carcinoma, which was composed of conventional low-grade adenoid cystic carcinoma with tubular and cribriform patterns, and a dedifferentiated carcinoma component (poorly differentiated adenocarcinoma). Immunohistochemical study showed that mammalian target of rapamycin and 4E-BP1 were expressed in both components; however, phosphorylated 4E-BP1 was expressed only in the dedifferentiated carcinoma component. This report clearly demonstrates that mammalian target of rapamycin pathway proteins were activated in dedifferentiated carcinoma. Mammalian target of rapamycin is a central protein involved in carcinogenesis, and administration of its inhibitors prolonged survival in some types of carcinoma. Therefore, mammalian target of rapamycin inhibitors may be a potential candidate for treatment of this highly aggressive carcinoma.