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Figure 1: Series of head (axial T2-weighted turbo spin echo sequences) and spine (sagittal post-gadolinium T1-weighted turbo echo sequences) MR examinations. A 12 year-old male presented with a lobulated neoplastic pineal mass (A1; arrow), biopsy-proven to be a yolk sac tumour, approximately measuring 4 x 2.5 x 4 cm (ap tr cc/ob), markedly vascularised but non-high-cellular, and containing a couple of subcentimetric central cystic foci. This lesion compressed and distorted the third ventricle causing moderate obstructive hydrocephalus and exerted mass effect also onto the right dorsal medial thalamic nuclei and onto the ipsilateral dorsal midbrain along its aqueduct. No intracranial or spinal metastases at baseline (A2). Favourable response to chemotherapy and radical VMAT therapy was achieved 7 months after diagnosis with a minimal cystic residuum (B1; arrow) which has remained stable over time (C1, D1; arrow). However, 23 months after end of treatment a millimetric faintly enhancing leptomeningeal deposit overlying the cord at the level of T10-11 (B2; circle) developed. This resolved (C2) the following year, after completion of further chemotherapy, autologous stem cell transplant, and craniospinal irradiation and has not reoccurred (D2) to date, 5 years off treatment.
Figure 2: Yolk sac tumour from the second endoscopic biopsy. (A) Vacuolated tumor cells forming Schiller-Duval body around a blood vessel (haematoxylin and eosin). (B) Immunohistochemistry confirms focal positivity with alpha-fetoprotein (AFP).