This chapter focuses on the diagnosis of neurosurgical biopsy and resection specimens from the central nervous system (CNS) and within the cranial-spinal vault. First, it presents ways to identify and manage various surgical specimens and tools that help with this process. Then, it provides a reference guide first to reactive changes and then to major etiologic categories of disease processes: infectious, inflammatory, demyelinating, cerebrovascular, neoplastic, degenerative, and developmental diseases. Toxic, metabolic, and traumatic diseases are noted where appropriate. The focus is on diseases seen by the surgical pathologist.
The approach to diagnosis employed in this chapter relies principally on histologic evaluation of hematoxylin and eosin (H&E;)–stained sections, with incorporation of smear preparations, histochemical stains, electron microscopy, and immunohistochemical preparations as supplemental aids in diagnosis.
The pathologist should always know, at a minimum, the age and sex of the patient, the precise location of the targeted lesion, and imaging characteristics. Knowledge about past medical history (e.g., previous CNS or primary neoplasms, connective tissue disease, immunosuppressive disease) is critical to interpretation. Likewise, knowledge about preoperative therapy (e.g., corticosteroids, chemotherapy, radiation therapy, radiosurgery) is also critical to interpretation of findings (e.g., necrosis, vascular fibrosis).
Major categories of lesions of the brain, spinal cord, and meninges, such as solitary or multiple masses, cysts, vascular malformations, or abscesses, are likely to be recognized by imaging or upon viewing a gross specimen.
Any undefined lesion should be biopsied and inspected by both cytologic preparation and frozen sections. Cytologic preparations add fine nuclear detail and the presence or absence of (a) glial-type processes; (b) discohesiveness in pituitary adenomas, oligodendrogliomas, medulloblastomas, and lymphomas; and (c) “epithelioid” features, with cellular cohesion (suggesting junctions) in carcinomas.
Optimal management of a specimen requires knowledge of the aim of the procedure. Three major types of neurosurgical procedures routinely yield tissue: (a) primary biopsies, (b) secondary biopsies, and (c) therapeutic resections. A primary biopsy seeks a diagnosis. Secondary biopsies may try again to establish a diagnosis or monitor consequences of therapy. Biopsies can be performed using CT- or MRI-guided stereotactic needle biopsy or using an open technique. Therapeutic resections attempt gross total excision of lesional tissue. Individual cases may combine more than one procedure at a single operation. For example, open biopsy for diagnosis of an intramedullary spinal cord tumor may proceed directly to a therapeutic resection if the intraoperative evaluation suggests ependymoma.
Source: Sternberg’s Diagnostic Surgical Pathology