C91.50 Adult T-cell lymphoma/leukemia (HTLV-1-associated) not having achieved remission

Billable ICD-10-CM code, FY2026. Acts as a Complication or Comorbidity (CC) as a secondary diagnosis.

Applicable to

• Adult T-cell lymphoma/leukemia (HTLV-1-associated) with failed remission
• Adult T-cell lymphoma/leukemia (HTLV-1-associated) NOS

Applies from C91 Lymphoid leukemia

Excludes1 (never code together)

• personal history of leukemia (Z85.6)

Applies from C91.5 Adult T-cell lymphoma/leukemia (HTLV-1-associated)

Applicable to

• Acute variant of adult T-cell lymphoma/leukemia (HTLV-1-associated)
• Chronic variant of adult T-cell lymphoma/leukemia (HTLV-1-associated)
• Lymphomatoid variant of adult T-cell lymphoma/leukemia (HTLV-1-associated)
• Smouldering variant of adult T-cell lymphoma/leukemia (HTLV-1-associated)

Risk adjustment (HCC)

• CMS-HCC V28: HCC 19 — Myelodysplastic Syndromes, Multiple Myeloma, and Other Cancers
• CMS-HCC V22: HCC 10 — Lymphoma and Other Cancers
• RxHCC V08: HCC 19 — Leukemias and Other Hematologic Cancers
• ESRD V24: HCC 10

MS-DRG index

Defines the logic of DRG(s) 820-822 in MDC 17.

Approximate ICD-9-CM (GEMs)

• 204.80 Other lymphoid leukemia, without mention of having achieved remission (approximate)

Medicare Code Edits (MCE v43.1 (April 2026))

• Adult diagnoses (age 15 through 124): Age conflict edit. These diagnoses are clinically expected only in patients age 15 through 124.

Code annotations containing back-references to C91.50

Back-references to C91

• Type 1 Excludes: C76 Malignant neoplasm of other and ill-defined sites ("malignant neoplasm of lymphoid, hematopoietic and related tissue (C81-C96)")
• Type 1 Excludes: D72.8 Other specified disorders of white blood cells ("leukemia (C91-C95)")
• Type 1 Excludes: D72.825 Bandemia ("leukemia (C91.-, C92.-, C93.-, C94.-, C95.-)")
• Code First: M36.1 Arthropathy in neoplastic disease ("leukemia (C91-C95)")
• Code First: N16 Renal tubulo-interstitial disorders in diseases classified elsewhere ("leukemia (C91-C95)")
• Code First: R50.81 Fever presenting with conditions classified elsewhere ("leukemia (C91-C95)")
• Type 1 Excludes: T66 Radiation sickness, unspecified ("leukemia (C91-C95)")
• Code First: Z15.0 Genetic susceptibility to malignant neoplasm (", if applicable, any current malignant neoplasm (C00-C75, C81-C96)")

Nearby codes

• C91.4 Hairy cell leukemia
• C91.40 Hairy cell leukemia not having achieved remission
• C91.41 Hairy cell leukemia, in remission
• C91.42 Hairy cell leukemia, in relapse
• C91.5 Adult T-cell lymphoma/leukemia (HTLV-1-associated)
• C91.50 Adult T-cell lymphoma/leukemia (HTLV-1-associated) not having achieved remission (this code)
• C91.51 Adult T-cell lymphoma/leukemia (HTLV-1-associated), in remission
• C91.52 Adult T-cell lymphoma/leukemia (HTLV-1-associated), in relapse
• C91.6 Prolymphocytic leukemia of T-cell type
• C91.60 Prolymphocytic leukemia of T-cell type not having achieved remission
• C91.61 Prolymphocytic leukemia of T-cell type, in remission