Low-grade adenocarcinoma of the oral cavity. A comparison between the terminal duct and the papillary type.

Fifteen cases of a recently-described type of adenocarcinoma of salivary gland tissue are reviewed. Lesions are variously designated polymorphous low-grade adenocarcinoma, low-grade papillary adenocarcinoma, terminal duct carcinoma and lobular carcinoma. Tumours were divided into those with papillary structures (8 cases) and those without (7 cases), respectively low-grade papillary adenocarcinoma (LGPA) and terminal duct adenocarcinoma (TDA). Mean age of TDA-cases was 59.1 years; of the LGPA-cases 64.2-years. TDA's occurred anywhere in the mouth whereas LGPA's occurred in all but two cases in the hard palate. Three of the TDA-patients exhibited recurrent tumours as did 1 of the LGPA-patients. Metastatic disease was shown by 2 of the LGPA-patients. It is concluded that TDA and LGPA show sufficient difference in histopathological and clinical aspects to justify separating them. Both lesions are equally prone to local recurrence but it is the papillary type that can give origin to local and distant metastatic disease. The relation between LGPA and TDA on the one hand and adenoid cystic carcinoma on the other is discussed, leading to the conclusion that although there are some similarities, differences prevail.