C91.40
BillableHairy cell leukemia not having achieved remission
HCC Category Mapping
V28HCC 22 — Colorectal, Bladder, and Other Cancers
0.000V24HCC 10 — Lymphoma and Other Cancers
0.675ESRDHCC 10 — Lymphoma and Other Cancers
0.000RxHCCHCC 21 — Hodgkin Lymphoma and Other Cancers
0.000What This Code Means
A rare blood cancer (hairy cell leukemia) characterized by abnormal cells with hair-like projections that has not achieved remission.
Coding Tips
- •Hairy cell leukemia is a distinct subtype of lymphoid leukemia; verify diagnosis before coding
- •The fifth character '0' indicates no remission - document treatment response status
Clinical Significance
Hairy cell leukemia (HCL) is an indolent B-cell lymphoid neoplasm characterized by pancytopenia, splenomegaly, and distinctive 'hairy' cytoplasmic projections on malignant cells. Despite its indolent nature, untreated HCL can cause severe cytopenias and life-threatening infections. The 'not in remission' designation indicates active disease with ongoing bone marrow infiltration and potential symptomatic cytopenias.
Documentation Requirements
- ✓Documentation should include the characteristic morphology (hairy projections on light microscopy), immunophenotype (CD25+, CD103+, CD11c+, CD123+, Annexin A1+), and bone marrow biopsy findings showing a classic 'fried egg' pattern.
- ✓Disease status as not in remission must be explicitly stated, along with current blood counts showing cytopenias and spleen size assessment.
Commonly Confused Codes
C91.10 (B-CLL not in remission) is the most common misassignment, as both are indolent B-cell leukemias. HCL variant (HCLv) is a distinct entity with different immunophenotype and should be coded under C91.ZC91.90 (lymphoid leukemia, unspecified) should not be used when HCL is specifically diagnosed. Splenic marginal zone lymphoma (C83.0) may mimic HCL clinically.
Code Hierarchy
└C91Lymphoid leukemia└C91.4Hairy cell leukemia└C91.40Hairy cell leukemia not having achieved remission
└C91.40Hairy cell leukemia not having achieved remission