CSF and CNS Cytology

Abstract

The cytological examination of cerebrospinal fluid (CSF) and cytological specimens prepared from central nervous system (CNS) lesions plays a pivotal role in the diagnosis and management of CNS disorders, including tumors. The proper evaluation of CNS tumors typically includes a cytological touch preparation or squash preparation, used in conjunction with a frozen section during an intraoperative consult. Considering the potential wealth of information obtained, these cytological examinations constitute relatively simple and inexpensive investments in time and resources. Prompt evaluation and accurate interpretations are essential as patients can be acutely ill with infectious, neoplastic, or other disorders. The goal of this chapter is to provide a practical and illustrated approach to the interpretation of CSF and CNS cytology specimens. The first part of the chapter includes guidelines for the processing and examination of CSF and detailed descriptions of the microscopic findings, while the second part focuses on the practical aspects of brain tumor smear cytology. Smears of brain tumor tissue highlight important cytological features, such as nuclear detail and the presence of fibrillary extensions, that are critical to recognize when formulating a diagnosis and may be under recognized on frozen section; thus, as illustrated in this chapter, cytological smears are a valuable complement to frozen sections during intraoperative consultations.