ICD-10 Code C50.6 – Malignant neoplasm of axillary tail of breast (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code C50.6 – Malignant neoplasm of axillary tail of breast
What it is
C50.6 identifies a malignant tumor arising in the axillary tail of the breast, the portion of breast tissue that extends toward the armpit. Use it when documentation specifies this breast subsite.
Clinical signs
Findings may include a palpable breast or axillary-tail mass, local asymmetry, or imaging evidence of a suspicious lesion in that region. Clinical features vary; refer to documentation.
When to use this code
Use C50.6 when the provider documents primary breast cancer in the axillary tail, including pathology or imaging-supported diagnosis. Code it when the site is clearly stated and not described more generally as breast, upper outer quadrant, or axilla. If laterality is documented elsewhere, capture it as directed by the record.
Do not use for
Do not use this code for benign breast lesions, metastatic disease to the breast, or cancers described only as axillary lymph node involvement. Check documentation if the primary site is uncertain.
Coding tip
Confirm the exact anatomic site in the operative note, pathology report, or assessment before assigning C50.6.