ICD-10 Code C84.A0 – Cutaneous T-cell lymphoma, unspecified, unspecified site (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code C84.A0 – Cutaneous T-cell lymphoma, unspecified, unspecified site
What it is
This code identifies a cutaneous T-cell lymphoma when the subtype and involved skin site are not specified. Use it for a confirmed skin-based T-cell lymphoma diagnosis with incomplete documentation.
Clinical signs
Clinical features vary; refer to documentation. Commonly noted findings include persistent skin lesions, patches, plaques, or tumors, but the record should support a cutaneous T-cell lymphoma diagnosis.
When to use this code
Use C84.A0 when the provider documents cutaneous T-cell lymphoma without naming a more specific subtype or anatomic site. It also fits cases where the chart confirms the diagnosis but the pathology or note does not further define it. If the site or subtype is later clarified, you should code the more specific option.
Do not use for
Do not use this code for other non-Hodgkin lymphomas, B-cell lymphomas, or skin lesions without a confirmed lymphoma diagnosis. Check documentation if the record describes a specific cutaneous T-cell lymphoma subtype.
Coding tip
Query for the exact subtype and site when the note says only “cutaneous T-cell lymphoma,” because more specific coding may be available.