Table 4.

Structure of four-layered conclusion in the pathology report on CNS tumors with three examples

Four layers	Contents of the four layers	Example 1	Example 2	Example 3
1. Integrated diagnosis	Diagnosis based on integration of all tissue-based (especially histological and molecular) information	Diffuse astrocytoma, IDH-mutant (WHO grade II)	Diffuse astrocytic glioma, IDH-wildtype, with molecular features of glioblastoma (WHO grade IV)	Ependymoma, RELA fusion-positive
2. Histological diagnosis	Classification of tumor based on (immuno)histochemical evaluation	Diffuse astrocytoma	Anaplastic astrocytoma	Ependymoma
3. WHO grade	‘Standard’ histological WHO tumor grade	WHO grade II	WHO grade III	WHO grade II
4. Molecular information	Most important data from molecular analyses (e.g. sequencing, FISH, methylation profiling)	IDH1 R132H-mutant; ATRX-mutant; TP53-mutant	IDH-wildtype; TERT promoter-mutant; EGFR amplification	C11orf95-RELA fusion

Now that the definition of some CNS tumors is based on a combination of histological and molecular features, a layered reporting format of the conclusion in the pathology report helps to convey not only the message of the ‘integrated diagnosis’, but also provides in a nutshell the most relevant information on the ‘building blocks’ used to reach this diagnosis. Of note, the WHO grade in layer 3 is based on standard histological evaluation. In some situations this grade may be overruled by information obtained by molecular analysis (WHO grade IV instead of WHO grade III in the integrated diagnosis in example 2), in other cases, the WHO grade may be left out in the integrated diagnosis as assigning an unequivocal WHO grade is (still) difficult (example 3).