Hematopoietic Anatomy and ICD-O-3

Priority order for coding primary site

  • Hematopoietic Manual and/or Database
  • SEER Manual
  • ICD-O-3

NAACCR Item # 400: Primary Site (2580 Text-Primary Site Title)

Lymhoma can occur in any organ in the blood. The following table lists the bone marrow and lymphatic structures of the body. The lymphatic structures are categorized as nodal regions (specifically for staging), but do not specifically meet the definition of “lymph nodes.” All other primary sites can be found in ICD-O-3.1.External Website Policy

See the Hematopoietic Manual, Appendix C for a comprehensive listing of lymph nodes and their regions.

ICD-O-3 Codes ICD-O-3 Preferred Term Comments
C024, C090-C099 Tonsils (adenoids, lingual tonsils) Staged as a nodal structure
C142 Waldeyer’s ring Staged as a nodal structure
C379 Thymus Staged as a nodal structure
C421 Bone Marrow Assign primary site to bone marrow for the following
  • Leukemias
  • Myeloproliferative neoplasms
  • Myelodysplastic neoplasms
  • Plasma cell myeloma
C422 Spleen Staged as a nodal structure
  • Note that splenic involvement is usually due to dissemination of disease and not primary site.
  • Spleen is staged as a nodal structure when it is the only organ involved. Regional nodes for spleen, plus bone marrow and peripheral blood may also be involved.
C770 Lymph nodes of Head and Neck Most common (but not limited to)
  • Cervical lymph nodes
  • Retropharyngeal lymph nodes
  • Scalene lymph nodes
  • Supraclavicular lymph nodes
C771 Intrathoracic Lymph Nodes Most common (but not limited to)
  • Bronchial lymph node
  • Diaphragmatic lymph node
  • Hilar lymph node, NOS
  • Mediastinal lymph node
C772 Intra-abdominal Lymph Nodes Most common (but not limited to)
  • Abdominal lymph node
  • Celiac lymph node
  • Mesenteric lymph nodes
  • Para-aortic lymph nodes
  • Retroperitoneal lymph node
  • Splenic lymph node
C773 Lymph nodes of axilla or arm Most common (but not limited to)
  • Axilla lymph node
  • Brachial lymph node
  • Internal mammary
  • Pectoral lymph node
  • Subclavicular lymph node
C774 Lymph nodes in inguinal region or leg Most common (but not limited to)
  • Femoral lymph node
  • Inguinal lymph node
  • Sublingual lymph node
C775 Pelvic lymph nodes Most common (but not limited to)
  • Iliac lymph node
  • Obturator lymph node
  • Paracervical lymph node
  • Pelvic lymph node
  • Sacral lymph node
C778 Lymph nodes of multiple regions  
C779 Lymph node, NOS  

The following primary sites are NOT to be used for any hematopoietic neoplasms

  • C420: Blood
    • If a leukemia is diagnosed via a peripheral blood smear, primary site is bone marrow (C421), not blood
  • C423: Reticuloendothelial system, NOS
  • C424: Hematopoietic system, NOS

Note: Edits do prevent the use of these primary sites with the Hematopoietic histologies (9590-9993)

Updated: December 2, 2025