Masses of the pineal region: clinical presentation and radiographic features.

The pineal gland is important in structure, function and in the pathology that can affect it. The significance of the pathology of the gland and its adjacent structures is twofold: anatomical location, and biological behaviour of many of the lesions. The gland is in a critical anatomic location, and as the dorsal portions of the midbrain are compressed, patients may present with obstructive hydrocephalus, and/or with focal neurology. Masses and tumours of the pineal region range widely in behaviour, from the completely benign (eg, pineal cyst) to highly malignant (eg, pineoblastoma). Masses in the pineal region may be benign cysts (most common mass), tumours of various sources as well as rare vascular malformations that result in mass effect. Tumours of the pineal region represent a variety of histologies. Germ cell tumours are the most common: germinomas (50%), teratoma (15%), and choricocarcinoma (5%). Primary tumours of the pineal region make up 15% of all pineal tumours and represent a spectrum of aggressiveness. Other less common tumours also occur in the pineal region including metastatic spread and direct invasion from tumours arising in adjacent structures. Accurate diagnosis is essential to plan appropriate management, and early referral for medical imaging is a necessary first step. Although there is significant overlap in the imaging characteristics of some pineal masses, a distinction between aggressive and benign lesions is usually possible, and invaluable preoperative information is obtained in patients who require histological diagnosis.