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case_images: Pre-operative MRI of the brain. (A-C) MRI T1-weighted images with contrast demonstrating a heterogeneously enhancing lesion of the pineal gland. (D, E) MRI T2-weighted images with a T2 hypointense lesion with mass effect and compression of the cerebral aqueduct resulting in supratentorial ventricular dilatation and periventricular white matter signal abnormality. (F) MRI FLAIR image demonstrating periventricular transependymal flow of cerebrospinal fluid indicative of acute hydrocephalus. (G-I) MRI T1-weighted images with contrast demonstrating an enhancing lesion of the left cerebellar hemisphere.
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case_images: Subsequently, magnetic resonance imaging (MRI) revealed a heterogeneously enhancing lesion of the pineal gland with mass effect and compression of the cerebral aqueduct resulting in supratentorial ventricular dilatation with periventricular white matter T2 hyperintensity consistent with transependymal flow ( Figure 1 ).
case_images: Histopathology and immunohistochemical analysis of the pineal lesion. (A) Hematoxylin and eosin stain with nests and singly dispersed cells with a high nuclear to cytoplasm ratio (200x magnification). (B) Hematoxylin and eosin stain demonstrating a signet ring-like cell (arrow) (600x magnification). (C) Cytokeratin AE1 immunostain demonstrating strong reactivity (100x magnification).
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case_images: Pathology was consistent with poorly differentiated carcinoma ( Figure 2 ).
case_images: Whole-body PET scan. Numerous hypermetabolic lesions identified including the pineal region and left cerebellar hemisphere, bilateral cervical chain adenopathy, mediastinal/hilar adenopathy, bilateral axillary adenopathy, left cardiophrenic lymph node and left adrenal nodule. No evidence of a primary lesion was depicted.
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case_images: Imaging demonstrated hypermetabolism of the known multifocal metastatic adenopathy; however, no evidence of primary malignancy was revealed ( Figure 3 ).
case_images: Basic diagnostic workup and treatment flowchart of a solitary pineal lesion.
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case_images: A basic diagnostic workup and treatment flowchart of a solitary pineal lesion without additional intracranial lesions on imaging is depicted in  Figure 4 .
case_images: Our diagnostic workup and treatment plan of the case described herein (i.e., suspected pineal region metastasis).
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case_images: Our diagnostic workup and treatment plan of the case described herein (i.e., suspected pineal region metastasis) is depicted in  Figure 5 .