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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 550 (Bladder, NOS excluding mucosa) to EOD Primary Site based on invasion into the bladder with no mention of mucosa. EOD Primary Tumor for cervix, Note 1, instructions are to use the extension information to code primary tumor in preference to a statement of FIGO stage when both are available. TNM staging is closely related to FIGO stage, and the surgical findings of bladder invasion NOS in this case should be used in preference to the statement of T4.

Code Primary Site to C480 (retroperitoneum). 

Endometrial tissue may "break away” from the uterus and implant throughout the pelvic and abdominal cavities. This can occur in patients who suffer from endometriosis. This tissue remains behind when surgical removal of the uterus is done. Common sites of implantation are colon, peritoneum, retroperitoneum, and bladder. These cells may become malignant. When the uterus is no longer present (patient had surgical removal), code the site where the carcinoma was identified.

The site-morphology combination of C480 and 8380/3 was designated as an unlikely site-morphology combination by the Cancer PathCHART expert pathologist review, as this is a rare type of tumor. Assign a value of 1 in the Over-ride Site/Type [2030] data item in order to pass the Primary Site, Morphology-Type, Beh ICDO3, 2024 (SEER) edit.

Abstract a single primary as 8272/3 (pituitary adenoma/PitNET) using the Malignant CNS and Peripheral Nerves Solid Tumor Rules, Rule M2, a single tumor is always a single tumor. Change the histology of the 2023 diagnosis to 8272/3. This scenario does not meet the criteria in the current rules for M5 in that it requires a resection as part of the criteria. Since the patient did not undergo resection for either diagnosis, the 2024 diagnosis may indicate recurrence or progression.

A diagnosis of pituitary adenoma only is still coded 8272/0 (this code is still valid). A diagnosis of pituitary adenoma/PitNET, PitNET, or pituitary neuroendorine tumor is coded 8272/3. Cabergoline is used to treat prolactinoma or high levels of prolactin but does not impact the PitNET.

Abstract two separate primaries, ET (9962/3) and primary myelofibrosis (9961/3) using the current Hematopoietic and Lymphoid Neoplasms (Heme) Manual and Database (DB), Rule M15, use the Heme DB Multiple Primaries Calculator. Also refer to the example in Rule M15. In 1998, though the ET was not reportable (9962/1), the patient was treated with chemotherapy as a malignant neoplasm (9962/3). The Calculator instructs us to code separate primaries for these two histologies.

ET may evolve into a secondary myelofibrosis, also known as post-essential thrombocythemia-myelofibrosis (post-ET MF). The diagnosis must be stated as post-ET MF; this would be a single primary.

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

Code the specific histology as stated by the pathologist according to the site-specific instructions in the Solid Tumor Rules. When the histology provides a subtype/variant in addition to the HPV histology codes, code the subtype/variant as it is important to capture this histology as in the example provided. the instruction to code the subtype/variant over 8085 or 8086 applies to the following sites: oropharynx, cervix, vagina, vulva, anus, and penis. A note will be added indicatng this in 2025. 

Per 2024 Cancer PathCHART expert pathologist review, morphology codes 8085/3 and/or 8086/3 are valid and applicable to head and neck, oropharynx, cervix, vagina, vulva, fallopian tube, anus, and penis (reference: Cancer PathCHART: Product Downloads and Timelines). Other coding resources will be updated to reflect these changes in 2025.

Report these high grade dysplasia of the following organs as stated below.

Stomach: Assign code 8148/2 glandular intraepithelial neoplasia, high grade using the Other Sites Solid Tumor Rules, Table 6: Stomach Histologies and as described in the WHO Classification of Digestive Tumors, 5th edition.

Small intestine and Esophagus: Assign code 8148/2 glandular intraepithelial neoplasia, high grade, using the Other Sites Solid Tumor Rules, Other Sites Histology Rules, Rule H4/H26. The following note is listed for both of these rules.

Note: This list may not include all reportable neoplasms for 8148/2. See SEER Program Coding and Staging Manual or STORE manual for reportable neoplasms

The Other Sites Solid Tumor Rules, Table 5: Esophagus Histologies and Table 7: Small Intestine and Ampulla of Vater Histologies will be updated to reflect this code as time permits.

Please understand that AJCC sets the standards for TNM Staging and the Cancer PathCHART (CPC) initiative sets standards for the validity of site and morphology combinations. The statement in the AJCC manual “8240 and 8249 are excluded for topography code C160” means that these two histologies are not staged using the AJCC Staging System. As with numerous other reportable entities that are not staged by AJCC, the case is reportable and a Summary Stage should be assigned. Combinations of C160 with 8240 or 8249 are valid site/histology combinations for registry reporting and should not be discouraged from use if they correspond to the pathologist’s diagnosis. This goes for any other similar note in the AJCC manual. All CPC standards are enforced via the Primary Site, Morphology-Type, Beh ICDO3, 2024 (SEER) N7040 and Histologic Type ICDO3, Primary Site, Date of Diagnosis (NAACCR) N4911 data quality edits. Registrars can also look up the validity of site and morphology combinations using the CPC*Search tool:  https://seer.cancer.gov/cancerpathchart/search/tool/. 

It is important to remember the following.

• ALWAYS code the tumor histology stated by the pathologist/physician
• NEVER change the tumor histology to assign TNM
• Not all tumors or histologies can be staged per TNM
• Cases that cannot be assigned TNM are assigned a summary stage

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