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SEER Inquiry System - Report
Produced: 11/14/2025 5:00 AM
Question 20250015
Inquiry Details
References:
#1: Solid Tumor Rules. Non-Malignant CNS, 2025 Update
#2: WHO Class CNS Tumors, 301-305. Solitary fibrous tumor
Question:
Solid Tumor Rules/Behavior--Brain and CNS: Why was the Behavior of solitary fibrous tumor (SFT)/hemangiopericytoma, WHO Grade 1 changed from /0 to /1 in the 2025 Solid Tumor Rules (STR) updates? See Discussion.
Discussion:
In previous STR versions and the ICD-O-3.2, SFT/hemangiopericytoma, WHO G1 is 8815/0 and only SFT/hemangiopericytoma, WHO G2 was 8815/1. However, Table 6 (Non-Malignant CNS, Specific Histologies, NOS, and Subtypes/Variants) was changed in the 2025 updates to indicate both G1 and G2 SFT/hemangiopericytoma are 8815/1.
No date range was provided for this change in the STR and the behavior of this tumor was not updated by the standard setters in other references (i.e., ICD-O-3.2). The behavior of G1 SFT/hemangiopericytoma was not updated in the 2025 ICD-O-3.2 updates. If the ICD-O-3.2 was the source of this change, should this have been documented in the 2025 NAACCR Implementation Guidelines? However, the 2025 NAACCR Implementation Guidelines indicates, "There are no ICD-O-3 changes for 2025." Is this behavior change in 2025 Solid Tumor Rules updates an error? Should the behavior of SFT/hemangiopericytoma, WHO G1 remain /0?
Answer:
For cases diagnosed 2025 and later: Assign behavior /1 for solitary fibrous tumor unless stated to be malignant.
A review by the Cancer PathCHART expert neuropathologists found behavior code /0 is incorrect and both solitary fibrous tumor grade 1 and grade 2 are coded as 8815/1. WHO Classification of Central Nervous System Tumors, 5th edition, assigns behavior as /1 and no longer recommends terms solitary fibrous tumor/hemagiopericytoma and hemagiopericytoma. The STR table is correct. Future updates to ICD-O should reflect this behavior.
WHO Classification of Tumours, Central Nervous System Tumours, 5th ed. was reviewed by the CPC expert pathologists for implementation for cases diagnosed January 1, 2025.
Reminder: Comparing the CPC Validity Status included in the 2024 CPC*Search to that included in the 2025 SMVL (that table that drives the edits) is incorrect. CNS Tumors were not reviewed for 2024 implementation, they were reviewed for 2025 implementation. There will be a 2025 CPC*Search and a /1 will be designated as a Valid.
