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Abstract a single primary using Breast Solid Tumor Rules, Rule M18, as none of the previous rules apply.

Undifferentiated carcinoma is a malignant epithelial tumour lacking overt evidence of a specific line of differentiation. Dedifferentiated carcinoma is composed of an undifferentiated carcinoma and a differentiated component. Dedifferentiated carcinoma (8020/3) as a morphology is associated with cancer of the endometrium and ovary rather than the breast.  Breast cancer shows a broad spectrum of morphology with extensive variation in histological type and grade, related to the complexity of carcinogenesis.  This includes initial genetic changes in the cell of origin, subsequent genetic and epigenetic alterations, and reprogramming that occur at various stages of development along with interaction of other factors that influence the process of differentiation.  This scenario likely represents the process of phenotypic change of a carcinoma at a later stage, better known as transdifferentiation.

Do not report superficial angiomyxoma (8841/0) or aggressive angiomyxoma (8841/0).  WHO Classification of Female Genital Tumors, 5th edition, defines deep (aggressive) angiomyoma as a benign, infiltrative, myxoid spindle cell neoplasm that occurs in deep soft tissue of the pelviperineal region.

Answer updated April 2025

A change in the subcategory for a hormone drug does not indicate the end of First Course of Treatment because different hormone therapies generally achieve the same result. For example, some forms of breast cancer are estrogen-dependent and the various subcategories of hormone drugs used to treat them, such as gonadotropin-releasing factor agonists, aromatase inhibitors and estrogen antagonists, all achieve the same result - to block estradiol effects in these tumors.

Similarly, a change in immunotherapy is not a new course of treatment.

However, if a change to hormone therapy or immunotherapy is due to a change in the patient's ER, PR, or Her2 status, this could signify a new course of treatment.

The instruction in the SEER Manual is specific to chemotherapy. Chemotherapy is the only systemic treatment for which a change in the subcategory of a drug indicates the end of First Course of Treatment, due to the fact that different chemical agents damage cancer cells in different ways and at different phases in the cell cycle.

Code AML with monocytic differentiation as acute myeloid leukemia, NOS (9861/3) per consultation with our expert hematopathologist.

Acute monoblastic and monocytic leukemia (9891/3) and acute myelomonocytic leukemia (9867/3) are distinct entities according to the WHO. "AML with monocytic differentiation" is a descriptive diagnosis, whereas, "Acute monoblastic and monocytic leukemia" are specific diagnoses. In the WHO Classification of Tumours, Central nervous system tumours (4th Ed) in 2016, WHO began integrating information on molecular alterations that provide significant prognostic implications and/or a therapeutic target into the histology code/term itself. As a result it is also important to look at the molecular testing because acute myeloid leukemias can have different molecular mutations that could result in coding to a different histology code. In this case, there was no other information regarding additional immunophenotyping, so that is why AML, NOS was assigned.  Acute myeloid leukemia with monocytic differentiation has been added to the Hematopoietic and Lymphoid Neoplasm Database as an alternate name for 9861/3.

The correct term is diffuse leptomeningeal glioneuronal tumor listed as a synonym in Column 2. 

We will add the term diffuse in Note 2, Column 1 with the 2025 updates. In the meantime, you can add "diffuse" to your pdf version until the update is published.

Report VIN II. The 2024 SEER Manual lists this as a separate diagnosis in the Reportability section under Malignant Histologies 1.a.x. 

Do not report this case of "adenocarcinoma spectrum lesions" based on the information provided in the absence of a more specific diagnosis. Do not report until/unless a definitive diagnosis of malignancy is made. "Adenocarcinoma spectrum lesion" covers a continuum of lung neoplasms from preinvasive lesions (atypical adenomatous hyperplasia and adenocarcinoma in situ) to invasive lesions (minimally invasive adenocarcinoma and invasive adenocarcinoma).

Should additional information become available, report the case and assign the histology code if a more specific histology is confirmed later. Use text fields to record the details.

When pre-operative therapies are given as part of a clinical trial, code as neoadjuvant treatment in the Neoadjuvant Therapy data item when the intent is neoadjuvant and/or when surgical resection follows the clinical trial therapies. 

In the example, neoadjuvant chemotherapy was recommended in the treatment planning and the patient had the planned resection after neoadjuvant treatment. The treatment effect outcome is based on imaging that reported no mass and as documented by the physician, pathologist in this case as complete response to the neoadjuvant therapy based on the resection.

Use code 3 (limited systemic exposure) when treatment does not meet the definition of neoadjuvant therapy in the data item, Neoadjuvant Therapy. Limited exposure occurs when the patient receives some therapy prior to surgical resection, but the treatment is not enough to qualify for a full course of neoadjuvant therapy with the intent to impact extent of surgical resection or other outcomes. While this type of treatment may given as part of a clinical trial, it mostly refers to short term treatments such as hormone therapy.

When neoadjuvant therapy is given prior to surgical resection that is planned (intended) or performed to improve outcomes, use Code 1 or 2. Because a clinical trial is a type of research study that tests new methods of screening, prevention, diagnosis, or treatment of a disease, the treatment regimens likely will not be incorporated in recommended guidelines until all phases of the trial are completed and approved by the U.S. Food and Drug Administration. ClinicalTrials.gov is available to learn more about clinical studies around the world.

Report malignant spindle cell neoplasms consistent with atypical fibroxanthoma as directed by Appendix E.1 of the 2023 and 2024 versions of the SEER Manual using 8830/3 (fibroxanthoma, malignant).

We will update the answer in SINQ 20190102.  While the Other Sites Solid Tumor Rules address coding an NOS and specific histology sub-type/variant, this situation is not specifically addressed. We will also review the rules.

In sites other than breast (see Breast Solid Tumor Rules M8/M9), Paget disease with underlying invasive disease is a single primary and the underlying histology is coded. Primary Paget disease of the vulva is uncommon, and we cannot create rules for all possible situations in the Other Sites module. A GYN specific module is in development, and we will look into adding a Paget-related rule. It will differ because Paget in breast is a different situation while Paget in the vulva is always adenocarcinoma.

Paget disease of the vulva is an in-situ adenocarcinoma of vulvar skin with or without an underlying adenocarcinoma (WHO Classification of Female Genital Tumors, 5th ed.). When there is a statement of “underlying” adenocarcinoma, it is a single primary as with Breast Solid Tumor Rule M8.