Terminal duct adenocarcinomas of salivary tissues. Terminal duct adenocarcinoma is recommended as an encompassing diagnostic designation for a preponderantly intraoral salivary gland carcinoma that has also gone under the names of polymorphous low-grade adenocarcinoma, lobular carcinoma, and low-grade papillary adenocarcinoma. The carcinoma is biologically low grade, with its papillary phenotype manifesting a more aggressive behavior than nonpapillary forms. 