ICD-10 Code C50.51 – Malignant neoplasm of lower-outer quadrant of breast, female (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code C50.51 – Malignant neoplasm of lower-outer quadrant of breast, female
What it is
This code identifies a malignant breast tumor located in the lower-outer quadrant of a female breast. Use it when documentation specifies that exact breast quadrant and laterality is female breast cancer.
Clinical signs
Clinical features vary; refer to documentation. Common findings in breast cancer include a palpable mass, breast asymmetry, skin or nipple changes, or an abnormal imaging result prompting biopsy confirmation.
When to use this code
Use C50.51 when the provider documents primary cancer in the lower-outer quadrant of the female breast. It is appropriate for confirmed malignancy, including pathology or imaging-supported diagnoses when the site is clearly stated.
Code this only when the anatomic location is specific. If the record says breast cancer without quadrant detail, or the site is uncertain, check documentation before assigning this code.
Do not use for
Do not use this code for benign breast disease, carcinoma in situ, or unspecified breast cancer. Also avoid it if the tumor location is not documented as the lower-outer quadrant.
Coding tip
Verify both the quadrant and that the neoplasm is malignant before coding; if the site is unclear, query the provider.