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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. 

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.

The NAACCR Annotated Histology List (AL) serves as an aid to registry software vendors for implementing annual histology changes. This file has been maintained by the Registry Plus team at CDC’s NPCR for several years and reflects modifications to ICD-O-3 implemented by North American cancer registries over time. Although this list is reviewed multiple times prior to posting, there is no guarantee of 100% accuracy. 

As such, the AL is not a substitute for referring to various standard-setter documents and implementation guidelines. In this instance, Medulloblastoma Desmoplastic SHH-activated and TP53-wildtype 9471 is across several resources: the Solid Tumor Rules, Malignant CNS and Peripheral Nerves module in Table 3, column 3  as a subtype/variant of Medulloblastoma NOS 9470; in the CNS WHO 5th Edition BB; and in the WHO IARC ICD-O-3.2 posted to  ICD O 3 Coding Updates (naaccr.org). Although the exact related term of Medulloblastoma, SHH-activated, NOS is not listed, the NAACCR Implementation Guidelines for 2024 recommend checking the 2024 ICD-O-3 Update Table 1 or 2 to determine if the histology is listed. If the histology is not included in the update, then review ICD-O-3.2 and/or Hematopoietic and Lymphoid Database and/or Solid Tumor Rules (MP/H).

The Cancer PathCHART initiative has been undertaken to address gaps such as this between standard setting resources. Having all the standard histology coding resources included in a single all-inclusive database enables alignment of morphology codes & terms included in the CPC*SMVL (Cancer PathCHART Site-Morphology Validation List), Solid Tumors Rules, ICD-O-3 Annual Updates, NAACCR Annotated Histology List as well as the WHO 5th edition Blue Books. Please see Cancer PathCHART - Tumor Site-Morphology Surveillance Standards Initiative for more information on the Cancer PathCHART initiative, and more specifically, see Transitioning the Annotated Histology List to Cancer PathCHART (naaccr.org).

Code as an oropharyngeal primary site and histology as solitary plasmacytoma (9734/3) based on consultation with our hematological expert.

The WHO Classification of Hematopoietic and Lymphoid Tissues defines multiple myeloma as "bone marrow plasma cell percentage >60%." There are several other factors, but the bone marrow involvement is the key point for your case. The pathologist also states that the bone marrow is consistent with "plasma cell neoplasm," which by itself is not the same as multiple myeloma.

This case has 5-10% involvement by plasma cell neoplasm. This does not meet the bone marrow qualifications for multiple myeloma and is consistent with the pathologist's statement that there is minimal bone marrow involvement.

We will be updating the Hematopoietic and Lymphoid Neoplasms Database and Manual to clarify this (2025 updates).

Abstract as bone metastasis for the first two examples. Abstract as both bone and brain metastasis for the third and fourth examples in the respective Mets at Diagnosis fields based on the description provided.

Report malignant spindle cell neoplasms consistent with atypical fibroxanthoma as directed by Appendix E.1 of the 2023 and 2024 versions of the SEER Manual using 8830/3 (fibroxanthoma, malignant).

We will update the answer in SINQ 20190102.  While the Other Sites Solid Tumor Rules address coding an NOS and specific histology sub-type/variant, this situation is not specifically addressed. We will also review the rules.

Assign histology code, 8077/2 (squamous intraepithelial neoplasia, high grade) for LIN III and for LIN II. ICD-O-3.2 lists squamous intraepithelial neoplasia, grade II and grade III as 8077/2 indicating it is reportable. ICD-O-3.2 does not list every site-specific type of intraepithelial neoplasia. Check the SEER manual for reportable and non-reportable examples.

Do not code Reblozyl (luspatercept) as treatment. Luspatercept is an ancillary drug approved to treat anemia associated with MDS but not the malignancy.

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 8742/2 (lentigo maligna) for “early lentiginous melanoma in situ.” ICD-O-3.2 lists the preferred term for 8742/2 as lentigo maligna (C44._).