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Assign histology as 9505/3.  WHO Classification of Central Nervous System (CNS) Tumors describe ganglioglioma as a well-diffferentiated and slow-growing glioneuronal neoplasm.  While WHO does not recognize the histology/behavior combination 9505/3, the 2021 CNS Solid Tumor Rules identify non-malignant tumors that have the potential of transforming to a malignant tumor (new primary).  Ganglioglioma (9505/1) is listed with the transformed histology and instructs us to code as anaplastic ganglioglioma (9505/3).

Assign 9380/1 for low grade glioma diagnosed 1/1/2018 forward and for low grade glioma diagnosed prior to 1/1/2018 assign code 8000/1 on the advice of our expert neuropathologists. The site/type combination of C71 _ and 9380/1 will flag histology/site/behavior edits which should be overridden.

Low grade glioma is an umbrella term or non-specific diagnosis, primarily seen on radiologic reports such as CT scans and MRIs. Often, the patient is actively followed with scans and surgical intervention delayed or not recommended. WHO Classification of Central Nervous System Tumors, 5th edition, does not recognize this term and indicates that tissue diagnosis (including genetic testing) is needed to provide a specific diagnosis. Since biopsy of these “neoplasms” is not routinely done, a definitive diagnosis is not available. Literature searches yielded conflicting information with some stating low grade gliomas are malignant with an indolent clinical course while others felt they were benign. Until such time as WHO proposes a code for this neoplasm, our expert neuropathologists recommend coding glioma, NOS with borderline behavior 9380/1. 

Assign code 9431/1 for angiocentric glioma. This has been corrected in the 2025 update. Angiocentric glioma was removed from the 9421/1 row and remains in its own row.

The correct term is diffuse leptomeningeal glioneuronal tumor listed as a synonym in Column 2. 

We will add the term diffuse in Note 2, Column 1 with the 2025 updates. In the meantime, you can add "diffuse" to your pdf version until the update is published.

Assign 8013/3 (combined large cell neuroendocrine carcinoma). There are two histologies present: large cell NEC and urothelial. Literature search found primary large cell NEC of the bladder is extremely rare with less than 20 reported cases. This case does not fall into the site-specific rules and given it's raity, a specific rule for this situation was not and will not be added to the Bladder rules. See #1, Example 2, in the general instructions for coding histology.

HGAP is listed as a separate classification and is not a subtype of the diffuse gliomas. WHO Classification of Tumors of the Central Nervous System, 5th edition, has two categories dealing with non-pediatric astrocytic tumors:

Adult-type diffuse gliomas

Circumscribed astrocytic tumors

HGAP falls into the second category as a result of updates to the 4th edition WHO classification in 2016 with advances in the role of molecular diagnostics with the 5th edition. All astrocytic tumors were previously grouped together whereas not all diffuse gliomas (astrocytic or not) are grouped together on the basis of growth pattern and behaviors, and shared IDH1 and IDH2 genetic status. The new classification separates astrocytomas that have a more circumscribed growth pattern, lack IDH gene alterations, and sometimes have BRAF mutations (i.e., pilocytic astrocytoma). The impact of molecular advances has driven classification changes as described in the 5th edition.

Review of site/histologiy combinations for CNS neoplasms is currently being performed by Cancer PathCHART experts. It's possible they will recommend HGAP be moved to a subtype/variant of astrocytoma, NOS. 

Updated February 2026

For cases diagnosed 2025 and later: Assign behavior /1 for solitary fibrous tumor unless stated to be malignant or have metastasized.

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.

The example used in Rule M15 of the Urinary Solid Tumor Rules should refer to Table 2. We will update this in the next revision of the Rules.

Assign code 9084/3. According to our expert pathologist consultant, this is a teratoma with a somatic-type malignancy. This code is the best choice even though it does not capture the mixed germ cell elements of the tumor, or the character of the somatic component (rhadomyosarcoma, PNET).There aren't enough histology code numbers to cover all of the possibilities. Use text fields to describe the specifics of this case.

This question was reviewed by an expert neuropathologist. He recommends coding these tumors to malignant tumor, clear cell type 8005/3.

He states: these tumors are extremely rare. In summary, CNS HGNET-BCOR represents a rare tumor occurring in young patients with dismal prognosis. Whether CNS HGNET-BCOR should be classified among the category of "embryonal tumors" or within the category of "mesenchymal, nonmeningothelial tumors" remains to be clarified. Because CNS HGNET-BCOR share pathologic features and characteristic BCOR-ITD with clear cell sarcoma of the kidney, these tumors may represent local variants of the same entity.