ICD-10-CM Code for Malignant Neoplasm of Upper Outer Quadrant of Left Breast, Female, Estrogen Receptor Positive, Stage 1B
The ICD-10-CM code is C50.412 for the malignant neoplasm of the upper outer quadrant of the left breast in a female patient.
Primary Diagnosis Code
- C50.412 specifically identifies malignant neoplasm of upper outer quadrant of left female breast 1
- This code captures the anatomic location (upper outer quadrant) and laterality (left breast) required for accurate documentation 1
Additional Required Codes for Complete Documentation
Estrogen Receptor Status
- Z17.0 should be added to indicate estrogen receptor positive status 1
- This code is essential for treatment planning and prognosis, as ER-positive tumors respond to endocrine therapy 2, 3
- ER positivity is defined as 1% or more cells staining positive on immunohistochemistry 2
Stage Classification
- Stage 1B breast cancer requires documentation of the specific T and N classification 1
- Stage 1B corresponds to either T0N1mi or T1N1mi (micrometastases in 1-3 axillary lymph nodes) 1
- Consider adding appropriate TNM staging codes if your documentation system requires granular staging detail 1
Clinical Context for Coding Accuracy
- The pathology report must document ER status through immunohistochemical evaluation using standardized methodology (Allred or H-score) 1
- Progesterone receptor (PR) and HER2 status should also be documented with separate codes if positive, as these influence treatment decisions 1
- Ki67 proliferation index, while not directly coded, helps classify the tumor into molecular subtypes (luminal A vs. luminal B) 1
Common Coding Pitfalls to Avoid
- Do not use unspecified breast codes (C50.919) when the specific quadrant is documented 1
- Always include the estrogen receptor status code (Z17.0) as it directly impacts treatment selection and reimbursement for endocrine therapy 1, 2
- Ensure the stage documented matches the pathologic findings; Stage 1B requires either micrometastases (N1mi) or small primary tumor with limited nodal involvement 1
- If HER2 status is negative, this does not require a separate code, but if positive, appropriate coding for HER2 status should be included 1