C84.03

HCC Category Mapping

What This Code Means

Mycosis fungoides is a type of blood cancer that starts in skin T-cells and has spread to the lymph nodes inside the abdomen. This is an advanced stage of the disease where cancer cells are found in the abdominal lymph node region.

Coding Tips

• •Verify documentation specifies the lymph node location as intra-abdominal; if lymph nodes are in other locations (peripheral, mediastinal, etc.), use different C84.0x subcodes
• •Mycosis fungoides requires staging information; ensure the stage is documented and coded separately if applicable, as this code alone does not capture disease stage

Clinical Significance

Mycosis fungoides with intra-abdominal lymph node involvement indicates significant disease progression with visceral lymph node spread. Abdominal lymph node involvement in mycosis fungoides is associated with advanced staging and poor prognosis, requiring aggressive systemic therapy. This presentation is uncommon and represents transformation from early-stage cutaneous disease.

Documentation Requirements

• ✓Skin biopsy confirming mycosis fungoides
• ✓Abdominal imaging (CT or PET/CT) documenting intra-abdominal lymphadenopathy
• ✓Pathologic confirmation of nodal involvement if biopsy obtained
• ✓TNMB staging reflecting visceral lymph node disease
• ✓Treatment plan addressing advanced-stage disease

Commonly Confused Codes