ICD-10 Code C50.312 – Malignant neoplasm of lower-inner quadrant of left female breast (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code C50.312 – Malignant neoplasm of lower-inner quadrant of left female breast
What it is
This code identifies a malignant tumor in the lower-inner quadrant of the left female breast. Use it when documentation specifies this exact breast site and laterality.
Clinical signs
Clinical features vary; refer to documentation. Common findings may include a breast mass, skin or nipple changes, or abnormal imaging and biopsy results confirming malignancy.
When to use this code
Use C50.312 when the provider documents primary cancer in the lower-inner quadrant of the left breast. It is appropriate for confirmed breast malignancy with clear anatomic location and laterality. If the record only says left breast cancer without quadrant detail, check documentation.
Do not use for
Do not use this code for benign breast disease, unspecified breast cancer site, or malignancy in a different breast quadrant. Check documentation if the note does not clearly confirm the lower-inner quadrant.
Coding tip
Verify both quadrant and laterality in the pathology, imaging, or provider note before assigning this code.