Cytologic features of pleomorphic xanthoastrocytoma, WHO grade II. A comparative study with glioblastoma.

Pleomorphic xanthoastrocytoma (PXA) is a WHO grade II astrocytic tumor of children and young adults. It is characterized by pleomorphic, atypical astrocytes. Atypia is so remarkable, that PXA can be easily misdiagnosed as malignant glioma. If confused with a high-grade glioma the neurosurgeon may not proceed with a complete resection. Therefore, a specific recognition during intraoperative consultation is particularly important. We describe four cases of PXA evaluated during intraoperative procedures. Findings were compared with those of 22 glioblastomas. PXA smears were moderately cellular and showed a variable population of pleomorphic cells and fibrillary fragments with vessels. Tumoral cells were of intermediate size with a less frequent population of large, atypical cells. Some showed bi/trinucleation with bizarre nuclei. In two cases, tumoral cells with microvacuolization resembling xanthic astrocytes were present. No necrosis, mitotic activity, phagocytic macrophages or apoptotic fragments were seen. Smears from glioblastoma were more cellular than those of PXA with numerous neoplastic cells, branching vessels and myxoid substance. Cellular atypia was evident and mitoses were seen in all cases. Most cases showed an abundant population of accompanying macrophages and cellular debris. Differences between PXA and glioblastoma were related to cell turnover rather than cytomorphologic features. Glioblastoma shows features of high cellular replication showing a dirty background with necrosis and phagocytic macrophages as well as mitotic figures and apoptosis. On the other hand, smears from PXA have a clean background with no necrosis, cellular fragments or relevant mitotic activity. Diagn. Cytopathol. 2017;45:339-344. © 2016 Wiley Periodicals, Inc.