ICD-10 Code D03.121 – Melanoma in situ of left upper eyelid, including canthus (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code D03.121 – Melanoma in situ of left upper eyelid, including canthus
What it is
This code identifies melanoma in situ confined to the left upper eyelid, including the canthus. “In situ” means the malignant cells remain in the top layer of tissue and have not invaded deeper structures.
Clinical signs
Clinical findings may include a new or changing pigmented eyelid lesion with irregular borders, color variation, or asymmetry. Diagnosis is typically confirmed by pathology; clinical features vary, refer to documentation.
When to use this code
Use this code when documentation states melanoma in situ specifically involves the left upper eyelid, including the inner or outer canthus. It is appropriate after biopsy or excision when the pathology confirms in situ disease and laterality is documented.
Code it only when the provider identifies the lesion as melanoma in situ, not simply suspicious pigmentation or an unspecified eyelid neoplasm. If the site is not clearly stated, or the record says “check documentation,” verify laterality and exact eyelid location first.
Do not use for
Do not use this code for invasive melanoma, benign eyelid lesions, or melanoma in situ at another eyelid site or side. Check documentation if the canthus or laterality is unclear.
Coding tip
Confirm both laterality and the exact eyelid location in the pathology or operative note before assigning D03.121.