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This is a single primary with the histology coded as infiltrating duct and infiltrating lobular carcinoma [8522/3].

For cases diagnosed 2007 or later, the steps used to arrive at this decision are:

Open the Multiple Primary and Histology Coding Rules manual. For a breast primary, start with the Breast Multiple Primary Rules because there are site specific rules for breast primaries.

Start at Rule M4 because this patient has multiple tumors in the same breast. The rules are intended to be reviewed in consecutive order within the applicable Module. Abstract a single primary as tumors that are lobular [8520] and intraductal or duct are a single primary.

Use the Breast Histology Coding Rules to determine the correct histology for these multiple tumors abstracted as a single primary. Start at Rule H20 as there were multiple tumors present but it is a single primary. Code the histology to 8522 [duct and lobular] when there is any combination of lobular [8520] and duct carcinoma.

The Note for Rule M10 indicates Table 1 and Table 2 are used to identify specific intraductal and duct carcinomas. Referring to Table 2 (Duct 8500/3 and Specific Duct Carcinomas) note that pleomorphic carcinoma is listed as a specific type of duct carcinoma. Pleomorphic is a word that describes the cellular appearance rather than a specific histology. It is coded when that is the only description/diagnosis given (pleomorphic carcinoma/pleomorphic duct carcinoma). In this case, both duct and lobular are describing the actual histologic types. Ignore the term "pleomorphic" and code the actual histologic descriptors, ductal and lobular. We will make appropriate changes to the breast rules in the MP/H revisions so this distinction is clear.

Code the histology to 8574/3 for Ductal carcinoma with neuroendocrine features.

Ductal carcinoma is also called "invasive breast carcinoma of no special type." WHO classifies Invasive breast carcinoma with neuroendocrine differentiation as 8574/3.

For cases diagnosed 2007 or later, comedo necrosis is not synonymous with comedocarcinoma. If no further information is available for this case, code as carcinoma in situ.

For cases diagnosed prior to 2018

Code as encapsulated papillary carcinoma, 8504/3; this is a synonym for intracystic carcinoma (WHO Classification of Tumors of the Breast). Stage this case as invasive.

Code to metaplastic carcinoma, 8575/3. According to our expert pathologist consultant, "The term 'metaplastic stroma' implies that at least a portion of the carcinoma has undergone a 'metaplastic' change from epithelial in appearance to 'stromal' in appearance. I assume this is what CAP means by 'Invasive mammary carcinoma with matrix production,' which the WHO equates to metaplastic carcinoma."

Abstract a single primary. Based on the information provided, this is a single tumor, and therefore a single primary, Rule M3. Code the histology to malignant phyllodes tumor.

According to our expert pathologist consultant, "The presence of a phyllodes tumor component identifies the whole thing as such. Stromal overgrowth/sarcoma is the usual identifier of malignancy in a phyllodes tumor. (If there were no phyllodes component we would be left with undifferentiated sarcoma, but that is not the case here. The diagnosis of malignancy in phyllodes tumor may be difficult/problematic when there is no overt stromal/sarcoma overgrowth as in this case.) As an aside, the behaviors of pure sarcoma and a phyllodes tumor such as we have here are similar, but we would lose the primary diagnosis if we just called this sarcoma."

For cases diagnosed 2007 or later, code 8523 [infiltrating duct mixed with other types of carcinoma] for

1. Infiltrating ductal carcinoma, mucinous type and

2. Infiltrating ductal carcinoma with features of tubular carcinoma

The infiltrating ductal types in Rule H12 are listed (8022, 8035, 8501-8508) and do not include mucinous or tubular. We cannot use this rule. The first rule that applies to these single tumors is H17, code to 8523. If you look up 8523 in the numerical morphology section of ICD-O-3, you will see similar examples included in the definition of this 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.

For a case diagnosed in 2003, code 8507/3 [Duct micropapillary carcinoma]. See Coding Complex Morphologic Diagnoses, revised August 2002, 3rd example on page 5 and page 3, #4.

For cases diagnosed 2007 or later, code 8507/3 [Duct micropapillary carcinoma]. Use rule H12.

Abstract a single primary using Rule M13. Assign 8523/3 using rule H29. The code for  invasive ductal carcinoma with tubular features (8523/3) is higher than the code for invasive lobular carcinoma (8520/3). H28 does not apply because 8523/3 is not included as a type of duct carcinoma on Table 2.