Unifocal Langerhans-cell histiocytosis

This code represents a rare neoplastic proliferation of Langerhans cells characterized by a single lesion or site of involvement. It is a localized form of Langerhans cell histiocytosis (LCH), distinct from more widespread presentations. The condition can affect various organs, including bone, skin, or lymph nodes, but is confined to one anatomical location.

Use this code when documentation specifies a diagnosis of Langerhans-cell histiocytosis that is clearly described as unifocal or solitary. This applies when diagnostic workup confirms LCH and imaging or biopsy indicates involvement at only one site. Supporting documentation should explicitly rule out multifocal or multisystemic disease.

• Carefully review documentation to confirm the "unifocal" nature of the LCH; avoid confusion with multifocal forms.
• Pay close attention to the Excludes1 notes to prevent incorrect co-coding with multifocal or multisystemic LCH.
• Ensure the physician's documentation clearly specifies the affected site (e.g., "unifocal LCH of the femur") to support the diagnosis.