ICD-10 Code C50.319 – Malignant neoplasm of lower-inner quadrant of unspecified female breast (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code C50.319 – Malignant neoplasm of lower-inner quadrant of unspecified female breast
What it is
This code identifies a malignant tumor in the lower-inner quadrant of a female breast when the side is not documented. Use it for a confirmed breast cancer diagnosis limited to that specific breast region.
Clinical signs
Findings may include a palpable breast mass, skin or nipple changes, or abnormal imaging of the lower-inner quadrant. Clinical features vary; refer to documentation for laterality and pathologic confirmation.
When to use this code
Use C50.319 when the provider documents primary breast cancer in the lower-inner quadrant and does not specify right or left breast. It is appropriate after biopsy, pathology, or oncology assessment confirms malignancy. If laterality is known, code the specified side instead.
Do not use for
Do not use this code for benign breast disease, carcinoma in situ, or metastatic disease to the breast. Check documentation if the record describes a different quadrant or a specified breast side.
Coding tip
Verify both the quadrant and laterality in the pathology or oncology note before assigning this code.