Spontaneous Regression of the Pulmonary Metastases in Adenoid Cystic Carcinoma of the Parotid Gland: A Case Report.

Adenoid cystic carcinoma (ACC) is a rare epithelial tumor of the salivary glands with an indolent course and usually bears a long-term survival rate even when metastasized. Spontaneous regression of such a resistant tumor is an even scarce event. We report a case of a patient with ACC of the parotid gland with pulmonary metastases, which spontaneously resolved following resection and post-surgical radiation of the primary tumor. Among the numerous theories proposed to explain such a phenomenon, immunogenic mechanisms and the abscopal effect are the most plausible explanations in this case.