ICD-10 Code C50.21 – Malignant neoplasm of upper-inner quadrant of breast, female (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code C50.21 – Malignant neoplasm of upper-inner quadrant of breast, female
What it is
This code identifies a malignant breast tumor located in the upper-inner quadrant of the female breast. Use it when documentation specifies that exact breast quadrant and confirms cancer.
Clinical signs
Clinical features vary; refer to documentation. Commonly reported findings include a breast mass, skin or nipple changes, or imaging and biopsy results confirming malignancy in the upper-inner quadrant.
When to use this code
Use C50.21 when the provider documents primary breast cancer in the upper-inner quadrant of a female breast. It is appropriate for confirmed malignancy, including pathology-supported diagnoses and problem-list entries that clearly specify this site. If laterality or quadrant is unclear, check documentation before coding.
Do not use for
Do not use this code for benign breast disease, metastatic disease to the breast, or cancers in a different breast quadrant. If the record does not specify the upper-inner quadrant, check documentation.
Coding tip
Verify that the note states both malignancy and the upper-inner quadrant before assigning C50.21.