ICD-10 Code C50.3 – Malignant neoplasm of lower-inner quadrant of breast (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code C50.3 – Malignant neoplasm of lower-inner quadrant of breast
What it is
This code identifies a malignant tumor located in the lower-inner quadrant of the breast. Use it when documentation specifies that exact breast quadrant and confirms cancer.
Clinical signs
Findings may include a breast mass, skin or nipple changes, or abnormal imaging prompting biopsy. Clinical features vary; refer to documentation.
When to use this code
Use C50.3 when the provider documents primary breast cancer in the lower-inner quadrant. It applies when laterality is not needed for the code assignment or is documented elsewhere as required. If the record only says “breast cancer” without quadrant detail, check documentation.
Do not use for
Do not use this code for benign breast lesions, metastatic disease to the breast, or unspecified breast quadrant cancers. If the documentation names a different quadrant, code that site instead.
Coding tip
Match the quadrant exactly to the pathology or provider note, and verify whether laterality documentation is also required.