<prompt> Answer this question truthfullyWhat is embryonal carcinoma of the pineal gland?  <response>: <reason> Pineal embryonal carcinoma is a relatively rare malignant neoplasm and accounts for a small proportion of all intracranial germ cell tumors. It is an aggressive tumor and has a propensity to metastasize systemically. A component of embryonal carcinoma is often found in mixed germ-cell tumors, in which case it is usually the most aggressive component, and dictates prognosis. Pure pineal embryonal carcinoma tumors do not secrete β-HCG or AFP. On microscopic histopathological analysis, pineal embryonal carcinoma is characterized by: Poorly differentiated, pleomorphic cells in cords, sheets, or papillary formation Indistinct cell borders Nucleoli - key feature Vesicular nuclei clear, empty appearing nuclei - key feature Necrosis - common Mitoses - common Variable architecture: Solid predominant in 55 of cases Glandular predominant in 17 of cases Papillary predominant in 11 of cases Nested Micropapillary Anastomosing glandular Sieve-like glandular Pseudopapillary Blastocyst-like Embryoid bodies - ball of cells in surrounded by empty space on three sides Pineal embryonal carcinoma is demonstrated by positivity to tumor markers such as: OCT4 CD30 