Pineal region masses: differential diagnosis.

Most pineal region masses are malignant germ cell neoplasms that occur in young male patients. The most common is a germinoma, which is a homogeneous mass with signal intensity and attenuation similar to those of gray matter; the mass engulfs a densely calcified pineal gland. Teratomas are multilocular heterogeneous masses containing lipid areas. Other types of pineal region masses include choriocarcinoma, endodermal sinus tumor, and embryonal carcinoma. Pineal parenchymal neoplasms are usually either pineocytomas or pineoblastomas, which may "explode" preexisting pineal calcifications. Unlike the germinomas, they have no sexual predilection and may be seen in patients who are 20 years of age or older. Although the correct histologic diagnosis may be suggested with a careful evaluation of the morphologic features, attenuation, and signal intensity characteristics, very few of these tumors have a truly pathognomonic imaging pattern. Thus, histologic verification is necessary for most pineal region masses that appear to be neoplastic.