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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. 

Report this case of leukemia cutis and code to bone marrow (C421) and leukemia NOS (9800/3) based on the information provided. Update the abstract if new information becomes available.

Leukemia cutis is the rare infiltration of neoplastic leukocytes into the epidermis, dermis, or subcutis from an existing leukemia that results in clinically identifiable cutaneous lesions. Leukemia cutis may precede, follow, or occur concurrently with the diagnosis of systemic leukemia. It is an advanced phase of the leukemia having a poor prognosis that also strongly correlates with additional sites of extramedullary involvement. This can alter the appropriate treatment regimen for a patient. It is a type of "metastasis" or spread of the leukemia cells. The "conventional" definition for leukemia cutis is the infiltration of skin from a bone marrow primary. It is most often diagnosed via skin biopsy—punch, shave, etc., utilizing IHC/biomarker testing and is commonly associated with CMML and acute myeloid leukemia (AML). As such, it a reportable condition especially when preceding a confirmed systemic leukemia diagnosis. In this situation, the diagnosis date would be the date of the positive leukemia cutis skin bx—punch, shave, etc. The case should be coded to C421; 9800/3 Leukemia NOS until the official systemic leukemia diagnosis is rendered. If possible, follow back should be conducted to determine the specific systemic leukemia histology (CMML; AML) and the treatment received. If the leukemia cutis follows or occurs concurrently with the diagnosis of a systemic leukemia, it is NOT a separate primary but merely an advanced stage of the systemic leukemia diagnosis.

Abstract two primaries using Urinary Solid Tumor Rules, Rule M12. The histologies include non-invasive papillary urothelial carcinoma (8130/2) and non-invasive micropapillary urothelial carcinoma (8131/3). The two histology codes are listed as subtypes of Papillary urothelial (transitional cell) carcinoma in column 3 of Table 2.

WHO Classification of Urinary and Male Genital Tumors, 5th edition classifies micropapillary urothelial carcinoma as an aggressive subtype of urothelial carcinoma with carcinoma in situ present in more than half of all micropapillary carcinomas.

Rule 7 Note 3 of the Urinary Solid Tumor Rules states that there are no /2 subtypes for urothelial carcinoma with the exception of papillary urothelial carcinoma and applies to multiple occurrences of /2 urothelial carcinoma of the bladder.

Rule 8 applies to 8131/3 and 8120/3.

Report high grade serous intraepithelial neoplasm of the endometrium. 

Stop at the first rule that applies which is M12. Per note 3: When it is unknown/not documented whether the patient had a recurrence, use date of diagnosis to compute the time interval. This means there are two primaries.

There is a genetic syndrome that causes multiple carcinoid tumors in the GI tract, per our GI expert, and they should be treated as new primaries per M12.

SINQ 20110046 describes a unique situation whereby the subject matter expert felt that the occurrence of multiple tumors was due to an unknown underlying condition driving the proliferation of neuroendocrine cells.

A diagnosis of “tubulovillous adenoma with high grade dysplasia” in the duodenum is not equivalent to a diagnosis of “tubulovillous adenoma, high grade.”

Tubulovillous adenoma, high grade (8263/2) is not reportable as of 2022.

High grade dysplasia (glandular intraepithelial neoplasia, grade III) is reportable in the esophagus, stomach, and small intestine (8148/2).

Do not report angiomyxoma. ICD-O-3.2 assigns 8841/0 to this benign tumor. This includes superficial and deep (aggressive) angiomyxoma.

Lymphoepithelial carcinoma is a subtype of SCC usually seen in skin or H&N sites and often associated with EBV. CPC SME review determined 8082/3 invalid for breast but did not recommend a substitute code. There were only 45 cases coded 8082 2001 to 2019. For this case, it's possible the lesion originated in the breast skin and progressed to breast tissue. SCC is a subtype of metaplastic breast carcinoma so one could argue it code be coded either 8575 or 8070. For this case, we recommend assigning 8500/3. Use text fields to record the details.

Assign code 8461/3 for high-grade papillary serous carcinoma.

Many of these terms are not specified in the codes and definitions in ICD-10-CM. This is because ICD-10-CM does not have the same granularity as ICD-O-3.2. There are a few sites where intraepithelial neoplasia II and/or III are mentioned.

Even though ICD-O-3.2 classifies these as /2 (in-situ), for the intraepithelial neoplasia that are listed in ICD-10-CM, Grade II is designated as benign, while Grade III is designated as in-situ. It is not clear if medical coding will change the Grade II to an in-situ code.

All the in-situ codes (except cervix) are included in the casefinding list. Grade III is included with the in-situ codes; however, there is no guarantee that medical coders will code them as in situ. High grades are coded as in-situ in ICD-10-CM.

For those where there is no specific intraepithelial neoplasia code, the benign codes will cover any benign lesion for that site. This would make for a lot of review using the codes for casefinding. Most of the benign codes were removed from the casefinding list a couple of years ago to make it more manageable. 

Use the casefinding list as a guide for these neoplasias. It is not the most definitive source due to the lack of specificity of ICD-10-CM. It is not possible to map every single histology to a specific code. It is also not known how medical coders across the U.S. are coding these neoplasias. For that reason, pathology should remain the foremost casefinding resource used.

The casefinding team will need to review the prepared list below and determine what codes to add. Any updates will be incorporated in the FY2025 updates (October 2024.)