Histological Findings and Immunohistochemistry Patterns of Yolk Sac Tumour Arising in Sellar Region and Determining Endocrine Manifestations: a Case Report

Case Report: Yolk Sac Tumour (YST), also described as endodermal sinus tumour, is an aggressive non-germinatous malignant germ cell tumour composed of primitive germ cells arranged in various patterns, which can recapitulate the yolk sac, allantois, and extra-embryonic mesenchyme. About 80% of central nervous system germ cell tumours arise along a midline axis extending from the pineal gland to the suprasellar compartment. The authors report a case of YST in a female patient, 55 years, presenting headache, nausea, vomiting, vertigo, and visual loss. Laboratory findings included pan-hypopituitarism and hypercalcemia. Computed tomography revealed a nodular tumor in the sellar region. Clinical hypothesis of pituitary adenoma was suggested, and the patient underwent resection of the process. On histological evaluation, a malignant neoplasm constituted by atypical epithelioid cells disposed in solid sheets and/or anastomosing cellular trabeculae was found. The lesion exhibited a high mitotic index and eccentrically constricted cysts. The process showed positive immunoexpression for alpha-fetoprotein, glypican-3, pan-cytokeratins, and podoplanin, and negative expression for SALL4, OCT3/4, CD117, PLAP, CD30, and beta-hCG. The diagnosis of YST was then established. Patient passed away due septic shock.

Discussion: YST compromising sellar region is an uncommon tumor which can resemble pituitary adenoma on radiological evaluation. Clinical presentation includes visual disturbance, mostly field defects, hypopituitarism, and Diabetes insipidus. YST may adopt a variety of morphologic guises and are capable of considerable intratumoral heterogeneity. Sinusoidal growth pattern and Schiller-Duval bodies are typical histologic findings. Hyaline globules may appear to reside within or between neoplastic cells and are visualized in periodic acid Schiff preparations. YST must be distinguished from germinoma, embryonal carcinoma, choriocarcinoma, and immature teratoma based.

Final Comments: Extragonadal germ cell tumors are rare and comprise 2–5% of all germ cell tumors. Pure YST arising in sellar region is rare and associated with a very poor prognosis. There are no definite radiological criteria to establish the diagnoses of YST, which is more commonly a iso/low-intensity masses with good heterogenous enhancement and perifocal edema. Histopathological confirmation is required for the final diagnosis.