II.1.9.5 Malignant Transformation - Benign/Borderline Brain and CNS Tumors

If a benign or borderline tumor transforms into a malignancy, abstract the malignancy as a new primary. If there is a change in WHO grade from a WHO I to a higher WHO grade, abstract as a new primary malignancy. If a malignant CNS tumor transforms into a higher grade tumor, do not change histology or grade and do not abstract as a new primary. This determination is made by the pathologist based on review of slides.

Example

Non-malignant WHO grade I to malignant WHO grade III.

Complete two abstracts, one for the non-malignant tumor and one for the malignant tumor.

Situation

Create new abstract?

Benign /0 to borderline /1

No*

Benign /0 to malignant /3

Yes

Borderline /1 to malignant /3

Yes

Malignant /3 to malignant /3

No*

WHO Grade I to Grade II, III, or IV

Yes

WHO Grade II to III or IV

No*

WHO Grade III to IV

No*

* Abstract as one primary using original histology and note progression in remarks.

 

 

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