PAEDIATRIC-07 IMAGING OF PINEAL REGION TUMOURS IN CHILDREN

Abstract

Abstract Pineal tumors comprise between 3% and 8% of all pediatric brain tumors. Pineal region tumors can be divided into four categories: Germ cell tumors, pineal cysts, pineal parenchymal tumors, and tumors of the supporting tissues of the pineal gland or adjacent structures (such as pineal gliomas, dermoids, and epidermoids). The most common pineal region tumors are germ cell tumors, most are pure germinomas. Other variants such as nongerminomatous germ cell tumors, mixed germ cell tumors, teratomas, embryonal cell carcinoma, yolk sac tumor, and choriocarcinoma constitute the remainder. Germinomas are hyperdense on CT and enhance homogenously. The typical appearance on CT is a calcified pineal gland surrounded by noncalcified tumor. On MRI, these lesions have homogenous signal isointense to gray matter on all sequences with intense contrast enhancement. These tumors may infiltrate the thalami and midbrain. Spinal dissemination is seen in up to 36% of cases. Pineocytomas are well-differentiated tumors that retain morphologic features of the pineal parenchymal cells. They are slow-growing, circumscribed, but noncapsulated tumors. They are more commonly solid tumors, although cystic variants have been described. Solid tumors are either hypointense or isointense to gray matter and T2-hyperintense. Enhancement is homogenous and calcification is common. Cystic variants are often indistinguishable from pineal cysts. Pineoblastomas are malignant, unencapsulated tumors that resemble embryonal tumors NOS, but are distinct from such tumors in other locations due to their photosensory differentiation. On MRI, these lesions are hypointense to isointense on T1-weighted images and variable low, high, or mixed signal on T2-weighted images. They have lobulated contours and enhance homogenously. They calcify less often than pineocytomas. The “exploded pattern” of calcification with peripheral displacement of pineal gland calcification is considered more typical of pineal parenchymal tumors, differentiating them from germ cell tumors.