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Accession two primaries when a patient has synchronous, separate ductal and lobular tumors using Rule M13, Breast STRs, 2026 Update. Ductal carcinoma (8500/3) and lobular carcinoma (8520/3) are distinct histology terms and codes that are in different rows in Table 3. This is a modification of Rules M10 and H28 from prior versions of the STR Manual.

Assign histology as 8340/3 for IEFVPTC using the STR Manual, 2026 Update. Rule M18, Note 2, of the Other Sites STR state: Invasive encapsulated follicular variant of papillary thyroid carcinoma and Infiltrative follicular variant of papillary thyroid carcinoma share a histology code (8340) but are distinctly different entities. They are on separate rows of the table.

WHO Classification of Endocrine and Neuroendocrine Tumors, 5th ed., indicates that after classic PTC, the follicular variant of PTC (FVPTC) is the second most common histological subtype of PTC. Two major forms are known, infiltrative FVPTC and invasive encapsulated FVPTC. The majority of follicular PTCs are encapsulated FVPTCs, whereas infiltrative FVPTC is quite rare and clinically behaves like classic PTC.

Assign primary site as colon, NOS (C18.9) when the only information about the diagnosis you have is "colorectal cancer."

We consulted with a subject matter expert who believes that colon, NOS is closest to being correct and that rectosigmoid is not appropriate.

If further information becomes available through further workup and/or treatment, update the primary site as appropriate.

We will add clarification to the 2027 SEER Manual, Appendix C, Colon Coding Guidelines.

Assign code A280 for current unilateral oophorectomy with hysterectomy or with a previous history of hysterectomy.

We will remove the text ‘(salpingo-)’ from the Ovary surgery code A280 SEER Note in the next release of SEER Manual.

Report this case of spindle cell neoplasm with CLCN6::BRAF fusion based on the physician diagnosis of spindle cell sarcoma (8801/3).

CLCN6::BRAF is described as rare kinase fusion identified in a subset of spindle cell sarcomas. It is part of an expanding group of BRAF fusions in spindle cell neoplasms though it not extensively detailed in the literature. Along with other BRAF fusions, CLCN6::BRAF represents a potential oncogenic driver for targeted therapy.

Code sodium iodine (I 131) therapy in Radiation Treatment Modality as code 13 (Radioisotopes, NOS). Code Radiation External Beam Planning Technique as code 88 (not applicable). Do not code if used in diagnostic procedures.

Radioactive I 131 should be coded when given in therapeutic doses (usually 30-50mCi but could be higher in high risk patients). The same agent is used for diagnostic imaging, but the dose is very small (1-3mCi).

We will update SEER*Rx.

Armour thyroid is listed under "Thyroid" in SEER*Rx and in Appendix C Thyroid Coding Guidelines of the 2026 SEER Program Coding and Staging Manual. Code natural thyroid products as hormonal therapy in papillary, follicular, or oncocytic thyroid carcinoma. Thyroid histology must be known as coding depends on histology. Do not code if it is medullary or anaplastic thyroid carcinoma. If histology is unknown, assign Hormone Therapy as code 99.

In papillary, follicular, and oncocytic carcinoma, natural or synthetic thyroid hormone products have a dual role:

1. Suppression of thyroid stimulating hormone (TSH): This is cancer directed therapy since the tumor cells of the above mentioned morphologies express TSH receptor. TSH is a trophic hormone that can promote tumor growth.

2. Hormonal replacement therapy to treat post-surgical or post-radiation hypothyroidism. C-cells in medullary carcinoma do not express TSH receptor, thus, TSH suppression would not be indicated. However, replacement hormonal therapy with synthetic or natural thyroid hormones post surgery is given to treat the post-surgical hypothyroidism. In operable thyroid anaplastic carcinoma, the goal of levothyroxine therapy is hormone replacement.

The Thyroid Coding Guidelines are being updated to include oncocytic thyroid cancer in the 2027 release of the SEER Manual.

Report this ovarian tumor as histology 8442/3. Our subject matter expert, a specialized pathologist who deems this case reportable, advises if a rupture occurs, the presence of borderline tumor cells in peritoneal fluid is considered true tumor spread and malignant. Both ICD-O-3.2 and ICD-O-4 classify this as behavior /1 (Serous borderline tumor, NOS); however, based on the matrix rule, you should be able to update the behavior to /3. If you cannot override or enter it into your software, please contact your vendor.

Cancer PathCHART guidance for 8442/3 in the ovary recommends using 8460/3 (Low-grade serous carcinoma) or 8461/3 (High-grade serous carcinoma). Code 8442/3 should be used only when the grade cannot be determined.

Assign a second primary as Acute Myeloid Leukemia, NOS (9861/3), per Rule M10, the first being polycythemia vera (9950/3). The physician states “consistent with transformation of the patient's known polycythemia vera to acute myeloid leukemia.” This is not the same thing as “Acute myeloid leukemia with myelodysplasia-related changes.”

The Heme DB states:

Do not automatically assign this histology (Acute myeloid leukemia with myelodysplasia-related changes (9895/3) if patient has a history of a myeloproliferative neoplasm (Myelodysplastic Syndrome [MDS], or Myeloproliferative Neoplasm [MPN]). Note: Polycythemia Vera is a Myeloproliferative Neoplasm (MPN). The pathologist must make the diagnosis of being myelodysplasia-related.

Updated June 2026

Code the first course of treatment as active surveillance. Chemotherapy is second course of treatment based on this scenario due to progression.

We will be adding clarification about this type of scenario to the treatment rules in the 2027 updates, which will be released October 2026.