Understanding ICD-10 Classification for Breast Cancer
Breast Cancer ICD-10
The International Classification of Diseases, Tenth Revision (ICD-10), is a standardized system used worldwide to classify and code diseases, health conditions, and related clinical findings. Breast cancer has a designated category within the ICD-10 system that organizes different types, locations, and characteristics of malignant tumours arising in breast tissue. These codes support statistical reporting, health system organization, epidemiological tracking, and standardized documentation.
ICD-10 codes do not diagnose breast cancer or indicate treatment plans. Instead, they provide a uniform method for classifying confirmed medical findings documented by healthcare professionals.
Understanding ICD-10 Classification for Breast Cancer
Breast cancer is primarily classified in the ICD-10 system under the C50 category, which encompasses malignant neoplasms of the breast. Each subcategory describes a specific region of the breast where a malignant tumour has been identified. These distinctions are important for documentation purposes and help organize clinical information across healthcare systems.
The C50 category includes:
Malignant neoplasm of nipple and areola
Malignant neoplasm of central portion of breast
Malignant neoplasm of upper-inner quadrant
Malignant neoplasm of lower-inner quadrant
Malignant neoplasm of upper-outer quadrant
Malignant neoplasm of lower-outer quadrant
Malignant neoplasm of axillary tail
Overlapping lesions of the breast
Unspecified breast location when the exact site is not documented
These categories help maintain consistency when classifying breast cancer across different hospitals, clinics, and healthcare databases.
Structure of ICD-10 Codes for Breast Cancer
ICD-10 codes for breast cancer follow the general structure of the C50 category:
C50.0 – C50.9
The second decimal digit indicates the anatomical location of the malignant tumour.
Examples include:
C50.0: Nipple and areola
C50.1: Central portion of breast
C50.2: Upper-inner quadrant
C50.3: Lower-inner quadrant
C50.4: Upper-outer quadrant
C50.5: Lower-outer quadrant
C50.6: Axillary tail
C50.8: Overlapping sites of breast
C50.9: Breast, unspecified
The “unspecified” category is used only when documentation does not include an exact site.
Laterality in ICD-10 Coding
ICD-10 allows documentation of laterality, meaning whether the tumour is located in the:
Right breast
Left breast
Bilateral sites
Unspecified side
Laterality supports clearer health records and helps distinguish multiple breast findings when present. It is especially useful for ongoing monitoring and follow-up evaluations.
In Situ Breast Cancer in ICD-10
In addition to malignant neoplasms, ICD-10 includes separate codes for carcinoma in situ of the breast under the D05 category. These codes refer to abnormal cell growth confined within ducts or lobules that has not invaded nearby tissue.
The D05 subcategories include:
D05.0: Lobular carcinoma in situ
D05.1: Intraductal carcinoma in situ (ductal carcinoma in situ, DCIS)
D05.7: Other specified carcinoma in situ of the breast
D05.9: Carcinoma in situ, unspecified
These codes help distinguish between invasive and non-invasive findings in breast tissue.
ICD-10 and Histological Variants
Breast cancer can also be classified using additional ICD-10 codes when the tumour has a specific histological type. These codes fall outside the C50 category because they describe cell characteristics rather than location.
Examples of histology classifications include:
Codes for ductal carcinoma
Codes for lobular carcinoma
Codes for medullary, tubular, or mucinous carcinoma
Codes for rare and uncommon breast tumour types
These histology codes are often used alongside C50 codes to provide a more complete clinical picture, although exact combinations depend on documentation.
ICD-10 and Secondary Malignant Neoplasms
When breast cancer spreads beyond the breast, ICD-10 includes additional categories under C77–C79 for secondary malignant neoplasms. These codes document metastasis to:
Lymph nodes
Bone
Liver
Lung
Other distant organs
The presence of secondary codes does not replace the primary breast cancer code; instead, they are used together to describe disease spread.
Importance of Specificity in ICD-10 Breast Cancer Coding
Clear documentation supports the accurate assignment of ICD-10 codes. Specific details that may appear in clinical records include:
Exact tumour location
Laterality
Histological subtype
Stage of disease (although staging is separate from coding)
Presence of in situ vs invasive components
Whether lesions are overlapping
Whether additional organs are involved
The ICD-10 system requires these elements to classify breast cancer accurately, but clinical evaluation—imaging, biopsy, and pathology—is essential before any classifications are assigned.
ICD-10 and Epidemiology
ICD-10 coding plays a central role in public health research. Large datasets compiled from coded records help track:
Incidence of breast cancer in different populations
Geographical patterns of diagnosis
Trends in tumour types and locations
Use of healthcare services
Comparisons across demographic groups
These data inform public health planning, screening resource allocation, and long-term studies on breast cancer trends.
ICD-10 Does Not Determine Treatment
A key principle of ICD-10 is that it classifies, not guides.
It does not:
Recommend treatment
Define prognosis
Provide survival predictions
Indicate treatment eligibility
Treatment decisions depend on multiple clinical factors outside the ICD-10 system, including stage, biomarkers, tumour size, and individual health considerations.
Key Takeaways
ICD-10 breast cancer codes organize breast cancer diagnoses using standardized categories. The C50 category describes malignant tumours according to their anatomical location. Separate codes classify carcinoma in situ and histological tumour types. ICD-10 also includes codes for secondary malignancies. These codes ensure consistent documentation and support health system analysis but do not diagnose, treat, or predict breast cancer outcomes. Clinical evaluation remains essential for determining the nature of breast abnormalities.
Disclaimer
This article is for informational purposes only and does not provide medical advice, diagnosis, documentation instructions, coding guidance, or treatment recommendations. Only qualified healthcare professionals can determine appropriate diagnostic classifications.