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SEER Inquiry System - Report
Produced: 04/16/2026 1:53 AM
Question 20170012
Inquiry Details
References:
ICD-O-3
Question:
Primary Site/Sarcoma--Breast: How should the primary site and stage be coded for osteosarcoma of breast? Is C509 correct or should the code be a different primary site? When assigning C509, the Collaborative Stage (CS) still pertains to breast cancer and AJCC stages it as a breast cancer and not as a sarcoma.
Discussion:
Answer:
Code primary osteosarcoma of the breast to breast, C500-C509. Not all site and histology combinations can be staged in CS or AJCC. 9180/3 of breast cannot be staged using the CS breast schema. Breast (C500-C509) cannot be staged using the CS soft tissue schema. The same is true for AJCC. You can stage this case using SEER Summary Stage.
Important: Do NOT change the primary site or histology code based on whether or not the case can be CS or AJCC staged. We need to know how many cases are unable to be staged because of their primary site and histology combinations.
