Pseudopapillary pattern in intra‐operative squash smear preparations of central nervous system germinomas

Although the morphology of central nervous system (CNS) germ cell tumours is very similar to that of gonadal germ cell tumours, some architectural changes may dominate the microscopic appearance of CNS germinomas leading to misdiagnosis at low-power magnification.We report five cases of CNS germinoma demonstrating delicate pseudopapillary fronds on squash smear preparations.The age of the patients ranged from 5 to 21 years (mean 14). Three were female and two male. Three patients presented with symptoms of diabetes insipidus, including polydipsia and polyuria, while absence seizures, meaningless speech, hemiparesia, weight loss, insufficient breast development, amenorrhoea and symptoms of raised intracranial pressure were also encountered depending on the location of the tumours. Tumours were located in the hypophysis in two cases and in the suprasellar region in three. During the intra-operative pathological consultation, evenly distributed pseudopapillary or papillary structures formed the dominant pattern in the squash preparations of all cases. The neoplastic cells were characterized by pale variably vacuolated cytoplasm, pleomorphic nuclei with irregular membranes, and several prominent nucleoli. Variable numbers of small lymphocytes were also found.Intracranial germinomas may commonly exhibit a pseudopapillary pattern on squash smears that may cause misdiagnosis as neoplasms with papillary morphology. Careful examination of cellular details is essential in order to reach the correct diagnosis.