SUN-279 A Rare Case of Atypical Rhaboid Teratoid Tumour with Germinoma Differentiation in a 59 Year Old Woman

Atypical teratoid/rhabdoid tumours (ATRT) are a rare class of central nervous system malignant tumours which are comprised of elements of ectoderm and mesoderm germ-cell layers, but exhibit microscopic similarity to skeletal muscle. These tumours are more commonly seen in pediatric patients, with few case reports recently describing adult patients with this condition, in particular middle-aged women.(1–3) We present the case of a previously healthy 59-year-old woman who was found incidentally to have a pituitary mass on CT head, with retrospective symptoms of headaches, polyuria, polydipsia, diplopia, and low blood pressure. At presentation, she was found biochemically to have pan-hypopituitarism with a left cranial nerve six deficit, with an MRI depicting a 19.5 x 22 x 11 mm suprasellar mass extending into the infundibulum and hypothalamus, with displacement of the optic chiasm; repeat imaging ruled out apoplexy. She was started on supplemental levothyroxine and hydrocortisone replacement therapy, and sent for urgent transsphenoidal resection, which was complicated afterwards by hypernatremia from diabetes insipidus. Preliminary reports were suggestive of germinoma given the diffuse presence of Oct 3/4 and C-kit, with a proliferation index of 99%; further cytology of lumbar puncture revealed no malignant cells. However, upon further pathological analysis, her tumour demonstrated loss of INI-1 expression, which is diagnostic of ATRT. Given the mixed features on immunohistochemistry, the final diagnosis was concluded as an atypical teratoid/rhabdoid tumour of the sella turcica with germinoma differentiation. A multi-disciplinary approach consisted of initial radiotherapy, with chemotherapy targeted towards a germinoma-type tumour, and pituitary hormone replacement including treatment for central diabetes insipidus. This represents a unique case of a rare tumour with germinoma differentiation in an older patient that has not been previously reported. References 1. Journal of Clinical Neuroscience 49 (2018) 16–21 2. Acta Neurochir (Wien) (2008) 150: 491–496 3. Surgical Neurology International 2014, 5:75