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Findings: Sagittal post contrast image of the brain demonstrates a round uniformly enhancing 1.8 cm pineal region mass. There is minimal anterior impression upon the basal cisterns with significant mass effect upon the mid brain tectum. Axial T2 weighted image of the brain demonstrates increased signal within the posterior aspect of the mid brain consistent with local mass effect.
Diagnosis: Pineal germinoma.
Discussion: Masses within the pineal region can produce symptoms such as headaches, seizures, as well as hydrocephalus secondary to obstruction of the cerebral aqueduct. In addition, patients may present with Parinaud syndrome which classically presents with paralysis of upper gaze. This syndrome is secondary to mass effect upon the quadrigeminal plate.
The differential diagnosis for masses within the pineal region include: germ cell tumors, pineal parenchymal tumors as well as gliomas. Germ cell tumors are by far the most common masses in the pineal region. Specifically, germinomas account for approximately two thirds of all germ cell tumors. Males are more commonly affected with the peak age of presentation in the second decade of life. Radiographically, germinomas are usually homogeneous masses with signal intensity equal to that of gray matter. Because germinomas lack a capsule, there is a high incidence of drop metastases. Germinomas are radiosensitive with a 5 year survival of approximately 75% following radiation treatment alone. Less common germ cell tumors within the pineal region include: teratoma, embryonal carcinoma as well as choriocarcinoma.
Pineal parenchymal neoplasms include pineocytoma as well as pineoblastoma. Pineocytomas are benign neoplasms while pineoblastomas are highly malignant tumors which are unencapsulated and often demonstrate drop metastases as well as extension into adjacent brain parenchyma. Pineal parenchymal tumors are much less common than that of germ cell tumors. However, differentiation between the two can be suggested by their calcification patterns. Pineal parenchymal tumors more commonly contain intrinsic calcifications and therefore demonstrate an "exploded" calcification pattern. On the other hand, calcifications seen with germinomas represent pineal gland calcifications engulfed by tumor.
Non-neoplastic masses in the pineal region include a pineal cyst which is usually an incidental finding, as well as lipomas.
References:
Osborn NG. Diagnostic Neuroradiology. Mosby, St. Louis; 1994:408-421.
Smirnitopoulos JG, et al. Pineal Region Masses: Differential Diagnosis.
Radiographics; May 1992;12(3):577-596.
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