Abstract
The Veterinary Cancer Guidelines and Protocols (VCGP) group has issued a protocol for CNS neoplasms of dogs and cats. 7 The document offers general guidelines that can be utilized in studies involving the biological behavior of primary and secondary CNS neoplasms. Although focused on companion animals (dogs and cats), investigators are encouraged, when possible, to adapt the protocol to other animal species. The protocol outlines recommendations for systematic documentation of patient information, recording clinical data, neuroanatomic localization, and diagnostic features of CNS neoplasms. The description of the affected anatomic site or sites and compartments in the brain, spinal cord, and/or adjacent tissues must be considered by the pathologist writing the autopsy or surgical biopsy report, given that the tumor location provides important information that may ultimately impact the diagnosis, prognosis, and potential treatment options for the affected patients. The use of standardized parameters and well-described methods will generate information that is more impactful for use across institutions in comparative neuropathology studies. The protocol also offers a review of the histologic hallmarks and immunohistochemical profile of each neoplasm to facilitate accurate diagnosis in a routine diagnostic setting.
We would like to reassure readers that the methods in the protocol are designed to be practical and not excessively burdensome, and many of the recommendations are for collection of information likely already being performed by most diagnostic pathologists. The protocol is published on the VCGP website and will be periodically updated with relevant peer-reviewed literature. Here we provide a brief overview of the major points of the first iteration of the protocol. For more details, readers are encouraged to consult the full document at www.vcgp.org.
Patient signalment
Brief but complete description of species, age, sex, and breed.
Anatomic site
A simplified but systematic determination of the neuroanatomic localization and local or remote effects of the neoplasm should be included.
Bones
Skull bones (supratentorial or infratentorial) and vertebral bones (cervical, thoracic, lumbar, sacral, vertebral canal).
Meninges
Brain (telencephalon, diencephalon, mesencephalon, metencephalon, myelencephalon, skull base) or spinal cord (cervical, thoracic, lumbar, sacral, vertebral canal).
CNS parenchyma
Brain (telencephalon, diencephalon, mesencephalon, metencephalon, myelencephalon, ventricles) or spinal cord (cervical, thoracic, lumbar, sacral, central canal).
Adjacent tissues
Cranial nerves, pineal gland, pituitary gland, spinal nerve roots.
Laterality
Unilateral lesion (specify side), midline lesion, bilateral lesion.
Other features
Neuroimaging findings, method utilized to collect the tumor sample (biopsy, autopsy), specimen size, presence of tumor infiltration, histologic tumor classification and grading (with mitotic count), tumor margin assessment, ancillary testing results, treatment, and patient outcome. Additional guidelines are available for margin evaluation and patient outcome assessment at the VCGP website.3,6
The classification and grading of most canine and feline CNS neoplasms is based on the Histological Classification of Tumors of the Nervous System of Domestic Animals and the World Health Organization (WHO) Classification of Tumors of the Central Nervous System.5,8 However, the veterinary classification and grading system has been largely extrapolated from the human literature and does not correlate with biological behavior of CNS neoplasms in domesticated animals. Thus, its use is of questionable importance for prognostication purposes. Additional studies using standardized prognostic parameters are needed to create grading schemes for canine and feline CNS neoplasms that are correlated to biological behavior and patient outcomes. The VCGP has published a grading guideline to aid authors in creating the most efficient and prognostically significant grading schemes possible. 2 Key criteria to grading systems encompass reproducibility within and across observers, relevance to prognosis, and realistic application in a routine diagnostic setting.
In addition, the human WHO guidelines rely heavily on molecular testing as an aid to histology and immunohistochemistry (IHC) for a more objective classification and grading of neoplasms. These laboratory tools are not yet widely available for veterinary pathologists, and thus the diagnostic characterization of CNS neoplasms of dogs and cats relies predominantly on tumor localization, routine histologic examination, and IHC of tumor samples obtained from biopsy or autopsy. For this reason, and until molecular tools are readily available in veterinary medicine, there is an urgent need for more objective and precise means to morphologically classify and grade CNS neoplasms that would reduce intra- and interobserver disagreement when examining tumor samples. Although efforts have been made to develop and apply updated classification and grading systems for specific groups of canine neoplasms,1,4 further studies are necessary to correlate tumor type and grade with clinical outcome and to establish their capacity to predict tumor behavior and prognosis. The CNS protocol is intended to aid investigators in their study design by providing a checklist of parameters for consideration.
