What is the ICD‑10‑CM code for a stage I malignant neoplasm located in the upper outer quadrant of the right female breast with estrogen‑receptor‑negative (triple‑negative) disease?

ICD-10-CM Code for Stage I Triple-Negative Breast Cancer, Upper Outer Quadrant, Right Breast, Female

The correct ICD-10-CM code is C50.411 (Malignant neoplasm of upper-outer quadrant of right female breast).

Primary Diagnosis Code

• C50.411 is the anatomic site-specific code for malignant neoplasm of the upper outer quadrant of the right female breast 1
• This code captures the precise anatomical location as specified in your clinical scenario 1

Essential Additional Codes Required

You must append additional codes to fully document this case:

Stage Documentation

• Add the appropriate clinical or pathological stage code from the TNM staging system (eighth edition AJCC) to specify Stage I disease 1
• Stage I breast cancer is defined as tumors ≤20 mm in greatest dimension (T1) with no regional lymph node involvement (N0) and no distant metastases (M0) 1

Receptor Status Documentation

• Z17.0 - Estrogen receptor negative status 1
• Z17.1 - Progesterone receptor negative status (implied by triple-negative designation) 1
• There is no specific ICD-10 code for HER2-negative status, but triple-negative breast cancer is defined by absence of ER, PR, and HER2 overexpression 1, 2, 3

Clinical Context for Coding Accuracy

Triple-negative breast cancer represents 10-20% of invasive breast cancers and is characterized by lack of expression of estrogen receptor, progesterone receptor, and absence of HER2 overexpression 1, 2, 4. This molecular profile has significant prognostic and therapeutic implications:

• TNBC is not amenable to hormonal therapy or HER2-targeted therapy (trastuzumab), limiting treatment options primarily to cytotoxic chemotherapy 3, 4
• It demonstrates more aggressive behavior with higher recurrence rates and peak risk of recurrence within 3 years of diagnosis 1
• TNBC is three times more common in women of African descent and in premenopausal women 1

Coding Pitfalls to Avoid

• Do not use C50.91 (unspecified site) when the specific quadrant location is documented 1
• Do not omit receptor status codes - these are critical for treatment planning and prognosis, as they determine eligibility for targeted therapies 1, 5
• Ensure stage coding reflects the eighth edition AJCC TNM system, which incorporates both anatomical and biological prognostic factors including tumor grade, ER, PR, HER2, and gene expression data when available 1
• Verify menopausal status documentation as this affects treatment decisions, particularly regarding ovarian suppression in premenopausal women with hormone receptor-positive disease (though not applicable in this triple-negative case) 1

Documentation Requirements

The pathological report must include confirmation via core needle biopsy with immunohistochemical evaluation demonstrating 1:

• ER negativity (using standardized assessment such as Allred score or H-score)
• PR negativity
• HER2 negativity (either IHC 0-1+ or ISH non-amplified per ASCO-CAP guidelines) 1
• Histological grade and Ki67 proliferation index for complete prognostic assessment 1