#1: Primary site
Source 1: 2021 SEER Manual
Notes: Appendix C, Breast Coding Guidelines
Primary site--Breast: Patient was diagnosed with invasive ductal carcinoma of the left breast. Site of mass is 2:00 to 3:00. What is the correct site code, C504 upper outer quadrant (UOQ) or C50.8 (overlapping)?
Assign C504, UOQ, for a left breast primary mass at 2:00 to 3:00. See the illustration in the SEER Coding Guidelines for breast, https://seer.cancer.gov/manuals/2021/AppendixC/Coding_Guidelines_Breast_2021.pdf