C96.6

HCC Category Mapping

What This Code Means

A rare cancer involving abnormal growth of Langerhans cells (immune cells) that is limited to a single site in the body.

Coding Tips

• •This code indicates disease confined to one location; confirm unifocal involvement is documented
• •Distinguish from C96.0 (multifocal/disseminated) which affects multiple sites

Clinical Significance

Unifocal Langerhans-cell histiocytosis, previously known as eosinophilic granuloma, is a localized proliferative disorder of Langerhans cells confined to a single anatomical site, most commonly bone. It generally carries a favorable prognosis with high cure rates after local treatment such as curettage or intralesional steroid injection. However, it requires monitoring because a subset of cases can progress to multifocal or multisystem disease.

Documentation Requirements

• ✓Documentation must confirm the diagnosis is limited to a single anatomical site (unifocal) with pathologic confirmation of Langerhans-cell histiocytosis through biopsy showing CD1a or langerin positivity.
• ✓The specific site of involvement, imaging confirmation of the solitary lesion, and treatment plan should be recorded.
• ✓Follow-up documentation should note stability or any progression to multifocal disease.

Commonly Confused Codes