Adenoid cystic carcinoma metastasizing before detection of the primary lesion

Although adenoid cystic carcinomas are occasionally manifested in atypical ways, metastatic disease preceding detection of the primary tumor has not been previously reported. We have described a patient in whom multiple pulmonary metastatic nodules were found one year before identification of primary adenoid cystic carcinoma of the maxilla. This case illustrates the need to include adenoid cystic carcinoma in the differential diagnosis of patients with metastatic disease and an unknown primary lesion. The use of special stains and electron microscopy can be helpful in confirming a diagnosis of adenoid cystic carcinoma.