De-differentiated metastatic adenosquamous carcinoma arising from germ cell tumor in the brain and spine.

Intracranial germ cell tumors have an estimated incidence of 0.4-3.4% in the Western Hemisphere. Patients can present with a variety of differing clinical signs and symptoms including headache, nausea/vomiting, hydrocephalus, obtundation, pyramidal tract signs, ataxia, and hypothalamic/pituitary dysfunction. Rarely germ cell tumors can transform into alternative malignancy. In these cases, treatment options may be difficult. Metastasis to the brain is not uncommon in germ cell tumors and is frequently reported within the pineal region; however, they are less common intraventricularly, within the posterior fossa and have never been reported after malignant transformation. Herein, we present the first reported case of a metastatic adenosquamous carcinoma transformed from a yolk sac tumor with diffuse cerebral metastasis in atypical locations of the brain including intraventricular and posterior fossa. A 53-year-old right-handed Caucasian female was transferred from an outside hospital for a chief complaint of altered mental status with CT head showing right side intraventricular mass and cerebellar hemorrhage. MRI of the brain found multifocal contrast-enhancing lesions of the right lateral ventricle, right cerebellum, right frontal lobe, diffuse lumbar dural enhancement, and an intramedullary lesion at the cervico-medullary junction of the brainstem. The right lateral ventricular lesion and right cerebellar lesions were resected. Pathology findings support a diagnosis of adenosquamous carcinoma, and the morphologic and immunophenotypic features suggest development as a somatic malignancy in a germ cell neoplasm with features of a yolk sac tumor. Germ cell tumors are typically included within the differential of pineal region masses; however, other locations such as intraventricular and posterior fossa are rarely seen. Even rarer are cases with malignant transformation to an alternative lesion for which treatment options are exceptionally scarce. Neurosurgeons and oncologists alike should be aware of this rare possible lesion to add to a broad differential diagnosis.