ICD-10 Code C84.40 – Peripheral T-cell lymphoma, not elsewhere classified, unspecified site (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code C84.40 – Peripheral T-cell lymphoma, not elsewhere classified, unspecified site
What it is
C84.40 identifies peripheral T-cell lymphoma, not elsewhere classified, when the site is not specified. Use it for a documented mature T-cell lymphoma that does not fit a more specific subtype.
Clinical signs
Clinical features vary; refer to documentation. Common findings in peripheral T-cell lymphoma may include lymphadenopathy, constitutional symptoms, or extranodal involvement, but you should code only what is documented.
When to use this code
Use C84.40 when the record confirms peripheral T-cell lymphoma, not elsewhere classified, and the provider does not document a more specific anatomic site. It is also appropriate when the diagnosis is established but the site remains unspecified in the note. Check documentation if another subtype or site is named.
Do not use for
Do not use this code for other non-Hodgkin lymphomas, B-cell lymphomas, or a more specific peripheral T-cell lymphoma subtype. If the site or histology is documented more precisely, code that information instead.
Coding tip
Verify the pathology wording carefully; if the report names a specific T-cell lymphoma subtype or site, select the more specific ICD-10-CM code.