CNS & pituitary tumors


Grossing, features to report & staging

Last author update: 1 January 2016
Last staff update: 19 November 2020

Copyright: 2002-2023,, Inc.

PubMed Search: Gross [title] CNS tumor

Nat Pernick, M.D.
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Cite this page: Pernick N. Grossing, features to report & staging. website. Accessed March 22nd, 2023.
Definition / general
  • Evaluate the arachnoid, gray and white matter
  • Section, if possible, from the arachnoid through the gray to the white matter
  • Sample interface between the lesion and normal appearing brain
  • EM helpful for poorly differentiated or unusual tumors (clear cell ependymoma), toxic - metabolic disease, infection; recommended to save tissue for EM in challenging cases
  • Infarcts: section perpendicular to surface of brain, submit sections of arachnoid, gray and white matter; save gray matter for EM if considering CADASIL or mitochondrial disease
  • Hematopoietic lesions: also B5, cell culture media (for flow cytometry), touch preparations, flash frozen tissue for molecular analysis
  • Infectious disorders: recommended that surgeon obtain cultures from sterile operating field
  • Toxic - metabolic disorders: recommend fixation of gray and white matter in formalin, glutaraldehyde, frozen tissue bank

  • Margins: usually impossible to assess due to piecemeal nature of resection or infiltrative growth pattern; may be able to determine for childhood pilocytic astrocytoma of cerebellum, cerebral dysembryoplastic neuroepithelial tumor and meningioma

  • Safety: recommended that surgeon contact lab if patient is HIV+ (use cytology, not frozen section) or may have Creutzfeldt-Jakob disease (decline frozen sections since cannot decontaminate cryostat); decontaminate cryostat used for HIV+ tissue by replacing blade, removing frozen debris and wiping surfaces with 10% bleach in water; for CJD specimens that are sectioned, recommended to place cassettes in formalin for 24 hours, then transfer to 100% formic acid for one hour, then return to fresh formalin for 48 hours, then process; label cassettes with pencil (formic acid dissolves ink), wrap needle biopsies in lens paper, handled embedded tissue as if infectious, dispose of blade, section waste, wipe microtome and cutting station with bleach, incinerate all towels, gloves and waste

Gross features of various disease entities
  • Abnormal mass: solid tissue not identifiable as gray or white matter
  • Cyst wall: flat tissue from 0 to 3 mm thick - compare to surgeon's impression or radiographs
  • Gliosis: often yellow or gray and firm
  • Necrosis: soft, friable, often cavitates
  • Semiliquid or gelatinous masses: usually tumors, including oligodendroglioma, lymphoma and pituitary adenoma
  • Vascular malformation: vessels larger than usual aggregate of arachnoid vessels, often associated with hemorrhage, may involve meninges or parenchyma
Intraoperative consult
  • Indications: (a) determine if lesional tissue is present, (b) determine if adequate sampling, (c) provide preliminary information to assist neurosurgeon (see below) and (d) perform special techniques (culture, B5 for lymphoma, touch preparations)
  • Need not give definitive diagnosis
  • Should not grade astrocytic glial neoplasm unless is clearly a glioblastoma (since tumors often have variable grades)
  • For some tumors, attempts at total resection are made (meningioma, schwannoma, solitary metastases, cysts, ependymoma, hemangioblastoma, cerebellar pilocytic astrocytoma, craniopharyngioma) so intraoperative consultation may be helpful
  • Recommended to assess undefined lesions by both frozen section and cytologic preparation
  • Cytologic preparation: adds fine nuclear detail, reveals glial type processes or epithelioid features of carcinomas; shows discohesiveness associated with pituitary adenoma, oligodendroglioma, medulloblastoma or lymphoma; may be more accurate than frozen section (Stereotact Funct Neurosurg 1995;65:187)
  • Recommended to obtain touch preparations (touch glass slide to wet tissue, fix before it dries, then stain)
  • Artifacts: long empty cavities in parenchyma (due to cryostat) vs. microcysts which contain cells and eosinophilic proteinaceous material)
  • References: Arch Pathol Lab Med 2005;129:1635, Arch Pathol Lab Med 1997;121:481, Mod Pathol 1988;1:378, J Neurol Neurosurg Psychiatry 1988;51:332, Arch Pathol Lab Med 2005;129:1653
Features to report
  • Specimen type
  • Specimen size (greatest dimension, additional dimensions are optional)
  • Tumor site
  • Tumor size (greatest dimension, additional dimensions are optional)
  • Histologic type
  • Histologic grade (WHO I - IV, other, cannot be determined, not applicable)
  • Margins (involved, uninvolved, cannot be assessed, not applicable)
  • Results of additional studies performed (electron microscopy, cytogenetics, molecular testing, immunohistochemistry)
  • References: Arch Pathol Lab Med 2001;125:1162

  • No TNM classification exists for CNS tumors (Edge: AJCC Cancer Staging Manual, 8th Edition, 2017) for these reasons:
    • For T component, histology and location are more important than tumor size
    • For N component, brain and spinal cord tumors do not propagate in lymphatics, so lymph nodes are not staged
    • For M component, metastatic disease is rarely seen (except for CSF seeding in some pediatric tumors) and extremely rare outside of the CNS
    • WHO classification and WHO grading systems should be used
    • Generally favorable prognostic factors: younger age, total resection versus subtotal resection; higher Karnofsky performance scale
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