Basal Cell Adenocarcinoma and Basal Cell Adenoma of the Salivary Glands: A Clinicopathological Review of Seventy Tumors with Comparison of Morphologic Features and Growth Control Indices

Basal cell adenoma and basal cell adenocarcinoma represent uncommon basaloid salivary gland neoplasms that show marked morphologic similarity. We wished to compare clinical outcome and morphologic features as well as growth and proliferation associated markers for both neoplasms. We reviewed the pathologic features of 70 neoplasms diagnosed as basal cell adenoma or basal cell adenocarcinoma. Observations included maximum mitotic activity and presence or absence of invasion into surrounding normal tissues as well as immunohistochemical studies for Ki-67, caspase 3, p53, and bcl-2. Establishing malignancy on the basis of invasion into surrounding benign tissues, 41 basal cell adenomas and 29 basal cell adenocarcinomas were identified. For tumors with follow-up, recurrence rates were 6.7 % for basal cell adenoma and 16.7 % for basal cell adenocarcinoma. One patient with basal cell adenocarcinoma had distant metastases and died of disease. Overall basal cell adenocarcinomas showed significantly higher values for growth and proliferation markers compared to basal cell adenomas. Salivary gland basal cell adenoma and basal cell adenocarcinoma show morphologic similarity. Basal cell adenocarcinoma can exhibit a locally aggressive behavior and has potential metastatic behavior. The overall mitotic rate and Ki-67 expression were higher in basal cell adenocarcinoma compared to basal cell adenoma, but overlap between the results of these observations in each tumor did not allow for accurate diagnosis or prediction of outcome in individual cases. We conclude that morphologic observation of local tissue invasion is the best marker for separating basal cell adenoma from basal cell adenocarcinoma.