Adenoid Cystic Carcinoma Metastatic to the Pituitary: A Case Report and Discussion of Potential Diagnostic Value of Magnetic Resonance Elastography in Pituitary Tumors

Adenoid cystic carcinoma (ACC) is an exocrine gland tumor accounting for approximately 10%-15% of all epithelial salivary neoplasms and occurs most often in the parotid and submandibular glands. Metastatic pituitary tumors are rare, and there is only 1 previously reported case of parotid ACC metastatic to the pituitary. Magnetic resonance elastography (MRE) is a dynamic magnetic resonance imaging (MRI)-based technique that measures the propagation of mechanically induced shear waves through a particular tissue to determine stiffness and offers a method to evaluate tissue consistency. We present the case of a 72-year-old woman with a remote history of parotid gland ACC and subsequent lung metastases presented after a fall that resulted in facial trauma. A non-contrast head computed tomography scan revealed a sellar/suprasellar mass, and follow-up MRI revealed a well-defined, enhancing 3.8-cm lesion. MRE showed the tumor to be firm. The tumor was resected through a transsphenoidal approach and was consistent with the MRE findings. Pathology returned as metastatic ACC. We report the second case of ACC metastatic to pituitary and the first firm pituitary tumor found by MRE and discuss the potential diagnostic value of MRE in pituitary lesions.