gms | German Medical Science

Objective: The diagnosis of gliomas has advanced with the 2016 World Health Organization Classification of Tumors of the Central Nervous System (2016 CNS WHO) and is now based on molecular parameters in addition to histology. Neuromolecular processing may put additional demands on quality and quantity of tissue samples and might challenge minimally invasive biopsy procedures. This study evaluates the diagnostic yield of glioma samples from frameless stereotactic biopsies with focus on molecular specifications.

Methods: All frameless stereotactic biopsy procedures from January 2011 to October 2017 were reviewed and patients with suspected or verified glioma were identified. Neuropathological samples were processed in accordance to 2016 CNS WHO standards including determination of IDH status for all glioma samples and 1p19q status for samples with oligodendroglial morphology. Applying the requirements of the 2016 CNS WHO diagnostic layers neuropathological diagnoses were reviewed and rated. Univariate analyses were performed to test the influence of procedural variables on diagnostic yield.

Results: 119 glioma patients out of a total of 180 consecutive frameless stereotactic biopsy procedures were identified over a period of 6 years and 10 months. A complete diagnosis according to 2016 CNS WHO including WHO grade and molecular information was achieved in 110 cases (92.4%). A histological description without definite classification of entity and WHO grade was present in four cases (3.4%). Four patients (3.4%) had an inconclusive histology. A diagnosis based on a first frameless stereotactic biopsy was proven wrong by the result of a second surgery sample in one patient (0.8%). Of the 110 complete diagnoses glioblastoma multiforme was present in 76 (69.1%), anaplastic astrocytoma in 25 (22.7%), diffuse astrocytoma in five (4.5%) and oligodendroglioma in four (3.6%) cases. Burr hole position, trajectory length, maximal tumor diameter, contrast enhancement, imaging modality, presence of frozen section and number of collected samples had no statistically significant impact on diagnostic yield (p > 0.05 in all univariate tests).

Conclusion: A complete diagnosis according to 2016 CNS WHO was achieved in the majority of cases. Frameless stereotactic biopsy seems to be an adequate diagnostic tool in contemporary neuro-oncology. The rate of inconclusive or erroneous biopsy results should be considered when consulting patients.