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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.

Code the histology to ductal carcinoma, NOS [8500/3] for a pathology report with a final diagnosis of "invasive carcinoma, no special type." Do not code the histology to carcinoma, NOS [8010/3].

The 4th Edition of the WHO Classification of Tumors of the Breast refers to invasive ductal carcinoma as invasive carcinoma, no special type. The ICD-O-3 code remains the same as invasive duct carcinoma [8500/3]. The next revision to the MP/H Solid Tumor Rules will clarify this issue.

When several diagnoses are made as part of the diagnostic process within two months, code the one with the worst prognosis.

Code the case example as acute myelocytic leukemia.

For cases diagnosed 2010 forward, refer to the Hematopoietic and Lymphoid Neoplasm Case Reportability and Coding Manual and the Hematopoietic Database (Hematopoietic DB) provided by SEER on its website to research your question. If those resources do not adequately address your issue, submit a new question to SINQ.

For cases diagnosed 1/1/04-12/31/06, code histology to 8524 [Lobular mixed with other types of carcinoma]. Assuming there is no mention of in situ, Histology Coding Rule 3 applies: Use a mixed histology code if one exists

For cases diagnosed 2007-2014, refer to the MP/H rules. If there are still questions about how this type of tumor should be coded, submit a new question to SINQ and include the difficulties you are encountering in applying the MP/H rules.

Malignant perivascular epithelioid cell tumor (PEComa) is reportable because it is malignant. Assign 8005/3 to malignant PEComa.

We consulted an ICD-O-3 expert who explained that some PEComas such as angiomyolipoma and lymphangiomyomatosis have specific ICD-O codes and their malignant counterparts may be coded to 8860/3 and 9174/3 respectively. There are no separate ICD-O codes for other specific PEComas, e.g., clear cell “sugar” tumor of lung, clear cell myomelanocytic tumor of the falciform ligament and some “unusual” clear cell tumors occurring in other organs—or for PEComa, NOS. These PEComas may therefore be coded to 8005 as clear cell tumors NOS; in other words as clear cell tumors that are not clear cell variants of carcinomas, sarcomas, or other specific tumor type.

Please note, PEComa is non-specific as to behavior. Unless the pathologist states that it is malignant, (as was the case for this question), the default code is 8005/1 (non-reportable).

Do NOT use the Collaborative Stage Manual to determine the histology code. For CS STAGING purposes only, coding should be based on the squamous cell carcinoma component of this tumor.

The Multiple Primary and Histology Coding Rules Manual is the correct source for coding histology. For cases diagnosed 2007 or later, the following steps are used to determine the histology code:

Open the Multiple Primary and Histology Coding Rules manual. For an esophagus primary, use the Other Sites Histo rules to determine the histology code because esophagus does not have site specific rules.

Start at Rule H8 because this is an invasive histology (assuming this is a single tumor). which states that one should code the appropriate combination/mixed code from Table 2 when there are multiple specific histologies.

Find Other Sites for Table 2 under the Terms & Definitions section of manual.

Locate the appropriate mixed code for squamous cell carcinoma and adenocarcinoma in column 1. Per column 3, the correct histology is adenosquamous carcinoma. Per column 4, the correct histology is 8560/3.

For tumors diagnosed prior to 2007:

Code Histology to 8255 [Adenocarcinoma with mixed subtypes]. This is a single tumor containing both a scar carcinoma and a bronchiolo-alveolar carcinoma--use 8255. The synonym for 8255 is adenocarcinoma combined with other types of carcinoma (not just subtypes).

For tumors diagnosed 2007 or later, refer to the MP/H rules. If there are still questions about how this type of tumor should be coded, submit a new question to SINQ and include the difficulties you are encountering in applying the MP/H rules.

Reportability for EIN became effective in 2021. 

1. Do not report atypical glandular epithelium. Atypical glandular epithelium, also referred to as atypical glandular cells (AGC), refers to abnormal looking cells that may be found in the tissue lining the inside of the endometrium or the cervix. While not malignant (in situ or invasive), they can be associated with a range of lesions in the female reproductive system.

2. Do not report isthmic-type mucosa with focal severe atypia. The NCI data dictionary defines atypia as an abnormality in cells in tissue. Report the case when further defined as atypical hyperplasia.

3. Do not report simple hyperplasia without atypia. WHO Classification of Tumors online, Female Genital Tumors (5th ed.), defines endometrial hyperplasia without atypia as a proliferation of endometrial glands of irregular size and shape without significant atypia. There is no ICD-O code for this term. Simple endometrial hyperplasia without atypia is an acceptable related term for endometrial hyperplasia without atypia. Pathology has priority over a physician statement.

4. Report EIN/CAH or focal EIN/CAH (8380/2) based on the biopsy. WHO Classification of Tumors online, Female Genital Tumors (5th ed.), defines EAH/EIN as a simultaneous change of epithelial cytology and an increased number of endometrial glands in a defined region. The preferred term is atypical hyperplasia of the endometrium; terms not recommended include complex atypical endometrial hyperplasia; simple atypical endometrial hyperplasia; endometrial intraepithelial neoplasia.

For cases diagnosed 2007 or later:

There are two primaries. Primary 1: The two tumors described on the pathology report from the lumpectomy are a single primary using rule M13. Primary 2: Disregard the foci of residual DCIS. Paget disease of the nipple is a separate primary using rule M12.

Primary 1: invasive mucinous adenocarcinoma and extensive ductal carcinoma in situ: Code the histology as 8480/3 [mucinous adenocarcinoma] using rule H27.

Primary 2: Paget disease of nipple: Code the histology as 8540/3 [Paget disease] using rule H14.