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SEER Inquiry System - Report
Produced: 10/23/2025 9:22 PM
Question 20240004
Inquiry Details
References:
#1: 2023 SEER Manual, Appendix E.1. see also 2024 SEER Manual
#2: Solid Tumor Rules. Other Sites, May 2023 Update
Question:
Reportability/Histology--Skin: Is a malignant spindle cell neoplasm consistent with atypical fibroxanthoma reportable for cases diagnosed 1/1/2023 and later, after thorough immunohistochemical work-up? See Discussion.
Discussion:
Appendix E1 in both the 2023 and 2024 SEER Program Coding and Staging Manual (SPCSM) lists these malignant spindle cell neoplasms, consistent with atypical fibroxanthoma, as reportable when other tumors have been ruled out with immunohistochemistry. This contradicts both SINQ 20190102 and the Solid Tumor Rules (STRs) general instructions indicating ambiguous terminology (e.g., “consistent with”) cannot be used to code the more specific histology when there is a NOS (malignant spindle cell neoplasm, 8004/3) and a more specific (malignant atypical fibroxanthoma, 8830/3) histology.
These tumors are typically diagnosed and treated in dermatology offices, so further chart review or confirmation by a physician is not possible for central registries.
As non-melanoma skin primaries are included in the Other Sites schema, and this schema was updated for cases diagnosed 2023 and later, which instruction applies to 2023+ diagnoses? Should these continue to be collected per Appendix E1 despite the conflict with the STR Manual and SINQ? If these are reportable, should the SINQ and STR Manual be updated to reflect this? Or should these be non-reportable per the STR Manual and SINQ?
Answer:
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.
