ICD-10 Code C91.6 – Prolymphocytic leukemia of T-cell type (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code C91.6 – Prolymphocytic leukemia of T-cell type
What it is
C91.6 identifies prolymphocytic leukemia of T-cell type, a rare mature T-cell leukemia. Use it when documentation specifies this exact hematologic malignancy.
Clinical signs
Clinical features vary; refer to documentation. Standard references describe leukemic blood involvement, often with lymphocytosis and enlargement of the spleen, liver, or lymph nodes.
When to use this code
Use C91.6 when the provider documents T-cell prolymphocytic leukemia, including confirmed or suspected cases recorded as the final diagnosis. It may also apply when pathology or hematology notes specify this subtype. If the record only says leukemia without type, check documentation.
Do not use for
Do not use this code for B-cell prolymphocytic leukemia or other leukemias with a different specified type. Do not assign it when the chart does not clearly identify T-cell prolymphocytic leukemia.
Coding tip
Code the leukemia subtype exactly as documented; if the cell type is missing, query the provider before assigning C91.6.