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Do not code as a treatment. Record the cessation of immunosuppressive drug treatment in text to explain the patient’s change in disease status.

Do not assign a behavior code of /2 to these cases unless you have a way to flag them so that they are not reported to the standard setters as in situ cases. Work with your state central registry to ensure that these cases are not unintentionally included in state case submission.

Report pheochromocytoma (8700/3). According to WHO Classification of Endocrine and Neuroendocrine Tumors, 5th edition, patients with pheochromocytomas are currently considered to have a lifelong risk of metastases and therefore conceptually they are all considered ‘malignant.’

Assign code 01 (White) for Race 1 when described as Indigenous-Latino/a or Indigenous-Latinx. Indigenous-Latinx is an umbrella term for Indigenous migrants to the United States from Latin America including South and Central America, the Caribbean, and Mexico (for example, Maya, Mixteco, Purépecha, Taino, Zapoteco, etc.). Latin America is listed in Appendix D of the 2025 SEER Manual as White.

Assign code 6 (Spanish, NOS; Hispanic, NOS; Latino, NOS) for Spanish Surname or Origin for Indigenous-Latino/a or Indigenous-Latinx in the absence of more specific information. Code 6 description includes the statement, There is evidence, other than surname or birth surname (maiden name), that the person is Hispanic but he/she cannot be assigned to any of the categories 1-5.

Assign code 03 (American Indian or Alaska Native) when described as First Nations. First Nations usually refers to Indigenous peoples for ethnic groups who are the original or earliest known inhabitants of an area. The term ‘First Nations’ can be applied to individuals, but technically refers only to those who have Indian status under Canadian law as part of a recognized community. Within Canada, the term First Nations is generally used for Indigenous peoples other than Inuit and Métis. Outside Canada, the term can refer to Indigenous Australians, U.S. tribes within the Pacific Northwest, as well as supporters of the Cascadian independence movement. 

Assign histology as squamous cell carcinoma, HPV positive (8085) for tonsil, NOS (C099) based on the positive HPV test. Codes 8085 and 8086 are valid for a select group of sites. The histology terms and codes that are valid for head and neck sites are included in the Head and Neck Solid Tumor Rules, Table 5 (oropharynx).

HPV detection tests that are used to identify HPV include DNA polymerase chain reaction (PCR), p16 (IHC), or DNA/RNA in situ hybridization. Assign the appropriate method of detection in the SEER data item, SEER Site-Specific Factor 1.  

Schema Discriminator 2 captures additional information needed to generate AJCC ID and Schema ID for some anatomic sites as stated in the SSDI Manual. For oropharyngeal cancer, a schema discriminator is used to discriminate between oropharyngeal tumors that are p16 positive, p16 negative, or p16 status unknown in order to assign the appropriate schema ID. Only the HPV p16 test can be used to assign Schema Discriminator 2. If another HPV test is performed, code 9. Override the edit for Schema Discriminator 2 when p16 is negative. Coding updates will be implemented in 2025.

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.

Sites may be added to certain combinations when indicated by ClinCORE review for Cancer PathCHART. Please note some sites were added in the 2024 update as a result of PathCHART review. A newly-formed Solid Tumor Editorial Board and its subgroups are currently working to evaluate the Solid Tumor Manual and make recommendations on ways to improve the structure and formatting of the manual and its content.

Follow the rules and instructions in the Other Sites STRs when assigning combination histology codes.

Histology Coding Rules

Use the Histology Coding Rules when assigning combination codes.

Coding Histology Information

Use this section that includes the mixed histology (Table 2) and site-specific histology tables (Tables 3-23) for one or more histologies within a single tumor. Do not use this section in place of the Histology Coding Rules.

While site-specific histology tables, based on current WHO Classification of Tumors books, have been added to Other Sites STRs, not all site groups have individual histology tables; coding may require the use of ICD-O and updates. The histology tables in Other Sites STRs include additional coding instructions and notes to assign the correct ICD-O code when appropriate.

The tables are not meant to be all-inclusive; rather they are intended to address difficult coding situations to facilitate the assignment of the correct histology code.

Table 2: Mixed and Combination Codes Instructions

Once you have identified the histology terms and have been instructed to use Table 2 by the Histology Coding Rules, compare the terms in the diagnosis to the terms in Column 1. When the terms match, use the combination code listed in Column 2. Use adenocarcinoma mixed subtypes 8255 as a “last resort” code.

Assign code 2, Neoadjuvant therapy started, but not completed OR unknown if completed, for the 2024 SEER Manual data item Neoadjuvant Therapy. Assign code 2 when neoadjuvant therapy was begun and the patient did not complete the full course of neoadjuvant therapy. See Coding Instruction #3 on page 230. The fact that the patient completed five cycles of the planned chemotherapy, but the sixth cycle was held due to neutropenia is important information and should be abstracted correctly and documented via text data items.

Assign code 8020/3 when the histologic type specifically includes the term of poorly differentiated, dedifferentiated, undifferentiated, or anaplastic undifferentiated carcinoma along with carcinoma as terms vary depending on the primary site. When the term poorly differentiated is included in the grade section only of the pathology report or only mentions poorly differentiated carcinoma without further substantiation from a pathology report as in examples 1 and 2, do not use code 8020/3.

The histology code 8020/3 and terms may be used for selected primary sites as included in the Solid Tumor Rules, WHO Classification of Tumors series (latest versions), and the Site/Morphology Validation List including

Nasal cavity

Nasopharynx

Salivary glands

Urinary sites

Colon, rectosigmoid, rectum

Esophagus

Stomach

Gallbladder and extrahepatic bile duct

Pancreas

Thyroid

Ovary

Uterine corpus

Vagina

Uterine cervix (also referred to as unclassifiable in WHO Classification of Female Genital Tumors, 5th ed.)

For sites other than those listed, if the diagnosis is poorly differentiated carcinoma, code 8010/3 and poorly differentiated in the grade field. 

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.