C91.41

HCC Category Mapping

What This Code Means

A rare blood cancer (hairy cell leukemia) with abnormal cells showing hair-like projections that has responded to treatment and is in remission.

Coding Tips

• •The fifth character '1' indicates remission status - confirm remission is documented
• •Hairy cell leukemia typically responds well to specific treatments; document treatment type if available

Clinical Significance

Hairy cell leukemia in remission indicates successful treatment response, most commonly following purine analog therapy (cladribine or pentostatin). HCL has one of the highest remission rates among hematologic malignancies, with complete remission achieved in 80-90% of patients after first-line therapy. Even in remission, long-term surveillance is required due to late relapse potential, sometimes occurring years to decades after initial treatment.

Documentation Requirements

• ✓Provider must explicitly state remission status, specifying complete versus partial remission.
• ✓Documentation should include normalized blood counts, resolution of splenomegaly, and bone marrow biopsy results showing absence of hairy cells.
• ✓The treatment that achieved remission, date of remission, and surveillance plan (including MRD assessment when performed) should be recorded.

Commonly Confused Codes