Optic nerve pilomyxoid astrocytoma: Intraoperative squash smear cytology of a rare entity

Pilomyxoid astrocytoma [PMA] is a rare, recently described variant of pilocytic astrocytoma with unique clinical and histopathological characteristics. It typically affects the optico‐chiasmatic and hypothalamic region in infants and young children. Though the pilocytic astrocytoma is the commonest tumor of the optic nerve, pilomyxoid astrocytoma arising from the intraorbital part of the optic nerve is extremely rare. To the best of our knowledge, only one case of introrbital optic nerve pilomyxoid astrocytoma has been described in the English literature. We report two cases of pilomyxoid astrocytoma arising from the intraorbital optic nerve, diagnosed on intraoperative squash smear cytology and later confirmed on histopathology. Like in other locations, optic nerve pilomyxoid astrocytoma behaves in an aggressive manner. The cytomorphological features of pilomyxoid astrocytoma recapitulate their histopathological characteristics. The presence of monomorphic piloid cells, angiocentric arrangement, myxoid background, absence of Rosenthal fibres and eosinophilic granular bodies helps to arrive at an accurate cytomorphological diagnosis of PMA.