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SEER Inquiry System - Report
Produced: 06/03/2025 10:20 PM
Question 20180074
Inquiry Details
References:
Solid Tumor Rules. Malignant CNS
Question:
Solid Tumor Rules (2018)/Multiple primaries--Brain and CNS: Rule M6 notes a diagnosis of glioblastoma multiforme is a new primary when it follows a diagnosis of a glial or astrocytic tumor. Does this rule apply if the subsequent diagnosis was just, glioblastoma, NOS or one of the subtypes/variants of glioblastoma multiforme? See Discussion.
Discussion:
Glioblastoma multiforme is listed as a synonym for the preferred term glioblastoma, NOS (9440) per Table 3 Column 2. Therefore, it seems reasonable to assume that a diagnosis of glioblastoma, NOS would be a new primary if it followed a glial or astrocytic tumor. However, in general, the Solid Tumor Rules use the preferred terminology and/or indicate when a specific rule also includes any tumor diagnosed as a subtype/variant. Rule M6 does not explicitly include a diagnosis of glioblastoma, NOS or any of its subtypes/variants (e.g., glioblastoma IDH-mutant or gliosarcoma). Does Rule M6 apply to any diagnosis of glioblastoma, NOS and any of its synonyms or subtypes/variants?
Answer:
Apply Malignant Central Nervous System Solid Tumor Rule M6 that refers to glioblastoma multiforme and abstract multiple primaries. If glioblastoma, NOS, an associated synonym with the same histology (9440/3), follows a glial or astrocytic tumor, Rule M6 applies.
With the identification of new variants of glioblastoma based on genetic profiles, we will likely see fewer diagnosis of GBM. M6 applies to cases where the subsequent/new tumor is specifically stated to be GBM, NOS.
