The lower-outer quadrant (LOQ) of the breast, though less commonly involved than the upper-outer quadrant, remains a significant site for breast cancer presentation. The ICD-10 code C50.511 is designated for confirmed cases of malignant tumors in the lower-outer quadrant of the right female breast.
This article serves as a complete reference for clinicians, medical coders, and oncology documentation teams. It explains when and how to use C50.511, clinical documentation requirements, SOAP examples, staging notes, and how to avoid miscoding. Plus, you’ll learn how DocScrib’s AI scribe tools help simplify oncology workflows.
When to Use ICD-10 Code C50.511
Use C50.511 if:
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A malignant tumor is confirmed (via biopsy or imaging)
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It is located in the lower-outer quadrant of the right breast
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The patient is female
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The quadrant is clearly documented through clinical exam or diagnostic imaging
This code reflects precise anatomical detail—an important requirement for cancer registry submissions and insurance billing.
Understanding Breast Quadrant Codes
| Location | Right Breast Code | Left Breast Code |
|---|---|---|
| Nipple and areola | C50.011 | C50.012 |
| Upper-outer quadrant | C50.411 | C50.412 |
| Lower-outer quadrant | C50.511 | C50.512 |
| Upper-inner quadrant | C50.211 | C50.212 |
| Lower-inner quadrant | C50.311 | C50.312 |
| Axillary tail (Spence) | C50.611 | C50.612 |
| Overlapping breast sites | C50.811 | C50.812 |
| Unspecified breast site | C50.911 | C50.912 |
Clinical Documentation Essentials for C50.511
To support this ICD-10 code, ensure the medical record includes:
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Confirmed diagnosis of breast cancer
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Tumor location: “lower-outer quadrant” and side “right breast”
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Imaging or biopsy results supporting quadrant-specific location
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Details like tumor size, grade, and histologic subtype (IDC, ILC, etc.)
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Receptor status: ER, PR, and HER2
Example Language for EMR:
“Patient presents with a 1.5 cm firm, irregular mass in the lower-outer quadrant of the right breast. Ultrasound shows a hypoechoic lesion at 5 o’clock, 3 cm from nipple. Core needle biopsy confirms invasive ductal carcinoma. ER+, HER2-.”
SOAP Note Example – C50.511
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S: “Patient reports noticing a small lump near the lower side of her right breast during self-exam.”
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O: Palpable mass in LOQ of right breast; diagnostic mammogram BI-RADS 5; ultrasound shows 1.4 cm lesion; biopsy confirms IDC.
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A: Malignant neoplasm of lower-outer quadrant of right female breast (C50.511)
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P: Order breast MRI, refer to surgical oncology, test for ER/PR/HER2, discuss lumpectomy vs. mastectomy.
Diagnostic Workup
| Modality | Purpose |
|---|---|
| Mammogram | First-line screening and localization |
| Ultrasound | Characterizes lesion and guides biopsy |
| MRI Breast | Assesses extent and multifocality |
| Biopsy (Core Needle) | Confirms malignancy and subtype |
| ER/PR/HER2 Testing | Determines treatment options |
| Genetic Testing | If family history or early-onset presentation |
Histological Subtypes Commonly Coded With C50.511
| Subtype | Documentation Tip |
|---|---|
| Invasive Ductal Carcinoma (IDC) | Most common, document grade and receptor info |
| Invasive Lobular Carcinoma | Specify clearly in pathology section |
| DCIS | Use D05.11 if cancer is in situ only |
| Triple-negative | Specify ER-/PR-/HER2- |
| HER2-positive | Consider adding trastuzumab to treatment plan |
Breast Cancer Staging (TNM System)
| Category | Criteria |
|---|---|
| T (Tumor) | T1 (<2 cm), T2 (2–5 cm), T3 (>5 cm), T4 (chest wall/skin) |
| N (Nodes) | N0–N3 based on axillary/supraclavicular node involvement |
| M (Metastasis) | M0 (none), M1 (distant metastasis) |
Treatment Planning
| Treatment Modality | Considerations |
|---|---|
| Surgery | Lumpectomy or mastectomy depending on size and location |
| Radiation Therapy | Post-lumpectomy or node-positive disease |
| Chemotherapy | Neoadjuvant for large or node-positive tumors |
| Endocrine Therapy | For ER/PR-positive tumors (Tamoxifen, Aromatase Inhibitors) |
| Targeted Therapy | For HER2+ tumors (e.g., Trastuzumab) |
Related ICD-10 Codes
| Clinical Detail | ICD-10 Code |
|---|---|
| Lower-outer quadrant, right breast | C50.511 |
| Family history of breast cancer | Z80.3 |
| Genetic susceptibility (BRCA1/2) | Z15.01 |
| Screening mammogram | Z12.31 |
| History of breast cancer | Z85.3 |
| Metastatic breast cancer | C79.81 |
Common Documentation Errors
| Error | Correction |
|---|---|
| Using C50.911 (unspecified site) when LOQ is known | Use C50.511 when quadrant is documented |
| Omitting breast side or quadrant | Always specify “right” and “lower-outer quadrant” |
| Failing to note receptor status | Document ER, PR, HER2 from pathology reports |
| Coding DCIS with invasive carcinoma | Use C50.511 for invasive; D05.11 for DCIS only |
FAQs
Can I use C50.511 for a male patient?
No. For males, use C50.521 (same quadrant, male gender).
Can this code be used if quadrant is suspected but not confirmed?
No. You must have clear clinical, imaging, or pathology documentation specifying the LOQ. Otherwise, use C50.911.
Should I also code Z17.0 for hormone receptor status?
Z17.0 can be used optionally to capture ER/PR status in oncology registries or quality reporting.
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Conclusion
ICD-10 Code C50.511 ensures precise documentation and reporting for breast cancers originating in the lower-outer quadrant of the right female breast. With accurate quadrant-specific coding, clinicians not only improve reimbursement and compliance but also enable better care planning. With DocScrib, these tasks are automated, faster, and smarter—so your team can focus on what matters most: the patient.