Primary Site--Colon: How is primary site assigned when the only documented term is “colorectal cancer?” See Discussion.
Patient is diagnosed with adenocarcinoma documented by the physician as “colorectal cancer.” The medical record does not specify colon, rectosigmoid, rectum, or any specific segment of the large intestine. There is also no imaging, operative, endoscopic, or pathology documentation identifying a more precise site of origin.
Specifically, should the registrar assign:
· C18.9 — Colon NOS - (excludes rectum, NOS C20.9 and rectosigmoid junction C19.9)
· C19.9 — Rectosigmoid junction
· C20.9 — Rectum NOS
· C26.0 — Intestinal tract, NOS
· C26.9 — Gastrointestinal tract, NOS
· or another site
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.
First Course Therapy/Hormone Therapy--Thyroid: Should Armour thyroid be coded as hormone therapy for a thyroid cancer case status post thyroidectomy at an outside facility who continues Armour thyroid at another facility? Armour thyroid is not listed in 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.
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