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Produced: 10/18/2026 11:33 AM
Question 20220021
Inquiry Details
References:
Solid Tumor Rules
Question:
Solid Tumor Rules/Multiple Primaries--Brain and CNS: How many primaries are accessioned, and what M Rule applies, for a 2012 diagnosis of left cerebral transitional meningioma (9537/0) that transforms to an atypical meningioma (9539/1) in 2022? See Discussion.
Discussion:
The patient underwent a resection of the transitional meningioma in 2012, but residual tumor was left behind. The patient was on surveillance until imaging showed growth of the residual tumor. The resection in 2022 proved atypical meningioma.
Rule M2, the first rule that applies, indicates this situation represents a single primary (a single tumor). However, Rule M4 states the transformation from a benign meningioma to a borderline meningioma would only be a single primary if the meningioma was a NOS.
This patient has microscopic confirmation of a meningioma showing different subtypes/variants (listed in Column 3, Table 6). Should this be accessioned as multiple primaries based on the transformation and distinctly different histologies?
Answer:
Non-malignant CNS rule M4 applies, this is a single primary. This scenerio is covered in Example 2: A meningioma 9530/0 transforms into an atypical meningioma 9539/1.
