MR Imaging of Pineal Cysts

PURPOSE: To evaluate the incidence and characteristic findings of pineal cyst incidentally detected on magnetic resonance(MR) imaging. MATERIALS AND METHODS: Brain MR images obtained in 2432 patients were retrospectively reviewed to determine the incidence and MR findings of pineal cysts, which were evaluated according to their size, shape, location, signal intensity, interval change, contrast enhancement and mass effect on adjacent structures. RESULTS: Cysts were encountered in 107(4.4 %) of 2432 patients evaluated. Their size ranged from 1 x 1 x 1 to 15 x 8 x 9(mean, 5.97 x 3.87 x 4.82)mm. All were spherical(n=53) or oval(n=54) in shape. Their margin was smooth and they were homogeneous in nature. On T1-weighted images, the cysts were seen to be hyperintense(n=57) or isointense(n=50) to cerebrospinal fluid, but less so than brain parenchyma. T2-weighted images showed them to be isointense(n=51) or hyperintense(n=56) to cerebrospinal fluid. The cysts were centrally located in 65 cases and eccentrically in 42. Compression of the superior colliculi of the tectum was demonstrated in 17 cases(15.9 %). No patients presented clinical symptoms or signs related to either pineal or tectal lesions. Peripheral enhancement around the cyst after Gd-DTPA injection was demonstrated in 51 cases ( 1 00 %). Follow-up examinations in 19 cases demonstrated no interval change. CONCLUSION: The incidence of pineal cysts was 4.4%. The MR characteristics of simple pineal cysts include: (1) an oval or spherical shape, (2) a smooth outer margin and homogeneous nature, (3) isosignal or slightly high signal intensity to cerebrospinal fluid on whole pulse sequences, (4) ring enhancement after contrast injection,(5) an absence of interval change, as seen during follow up MR study. These MR appearances of pineal cysts might be helpful for differentiating them from pineal tumors.

MR Imaging Findings of Pineal Germinoma: Focus on Differential Diagnosis from Other Germ Cell Tumors

PURPOSE: To determine the characteristic MR imaging findings of pineal germinoma, and differential diagnosisfrom other germ cell tumors. MATERIALS AND METHODS: MR images of patients with histopathologically proven pinealgerminoma(n=14) and other pineal germ cell tumors(n=10) were retrospectively analyzed with regard to size, signalintensity and homogenetiy, enhancing features, cyst formation, and multiplicity of lesions. Other pineal germ celltumors were the mixed germ cell tumors (n=4), malignant teratomas(n=3), choriocarcinoma(n=1), embryonalcarcinoma(n=1), and endodermal sinus tumor(n=1). Tumor markers were evaluated. RESULTS: On T1-weighted images,germinomas showed homogeneous(86%) or iso signal intensity(93%), while other germ cell tumors showedinhomogeneous(70%) or iso signal intensity(70%). On T2-weighted images, germinomas showed homogeneous(64%) or isosignal intensity(57%), while other germ cell tumors showed inhomogeneous(70%) or high signal intensity(80%). OnGd-DTPA enhanced images, germinomas showed homogeneous (93%) or strong enhancement(64%), while other germ celltumors showed homogeneous(60%) or strong enhancemant(70%). Cyst formation was noted in ten patients(71%) withgerminoma and in six(60%) with other germ cell tumors, Invasion of surrounding structures was seen in 11 patients(79%) with germinoma and in five(50%) with other germ cell tumors. Lesions were multiple in three patients(21%)with germinoma. Thirteen of 14 patients with germinoma had normal serum alpha-FP(tetoprotein) and beta-HCG(humanchononic gonafotrophin) levels. Two of four patients with mixed germ cell tumors had elevated serum alpha-FP andalpha-HCG levels; in the other two, elevated serum alpha-FP or beta-HCG levels were noted. In the malignant teratoma andembryonal carcinoma patients, serum alpha-FP and beta-HCG levels were normal. The patient with choriocarcinoma had anelevated serum beta-HCG level. CONCLUSION: On T1W1, the only significant differential point(P<0.01) betweengerminomas and other germ cell tumors was homogeneity. Germinomas were frequently homogeneous, and iso signalintensity on T1WI and T2WI, strong enhancement, and the formation of small cysts(<3mm) was noted. This MR imagingfinding, combined with assay for tumor markers, is helpful for the differential diagnosis of pineal germinoma andother cell tumors.