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Clinical Group


Derived from the IRS studies. Issues of concern are:

  • Amount of residual disease after diagnostic biopsy / resection when possible
  • Involvement of regional lymph nodes (N1)
  • Presence of distant metastases (M1)


GROUP I = Localized disease completely resected

The regional lymph nodes are not involved - lymph node biopsy or dissection is advised except in head and neck lesions. 

NB Complete resection must be confirmed by gross and microscopic examination of margins.  Any nodes taken with the specimen must be free of metastases.

Ia = Confined to muscle or organ of origin.

Ib = Contiguous involvement - infiltration outside muscle or organ of origin, as through fascial planes.


GROUP II = Total gross resection with evidence of regional spread

IIa = Grossly resected tumor with microscopic residual disease.  No nodal involvement

Surgeon believes that all disease has been resected, but the pathologist finds that there is tumor at the resection margin.  There must be no evidence of gross residual tumor and no evidence of regional lymph node involvement.

IIb = Regional disease with involved lymph nodes, completely resected with no evidence of microscopic residual.  (There is complete resection with histologic confirmation of negative resection margins.  Most distal node must be negative).

IIc = Regional disease with involved lymph nodes, grossly resected, but with evidence of microscopic residual and /or histologic involvement of the most distal regional lymph node from the primary site in the dissection.  The presence of microscopic residual disease makes this group different from Group IIb and nodal involvement makes it different from IIa.


GROUP III = Incomplete resection with gross residual disease

IIIa = After biopsy only.

IIIb = After gross or major resection of the primary tumor (more than 50%).


GROUP IV = Distant metastatic disease at onset

(To lung, liver, bones, bone marrow, brain, distant muscle and nodes.  This excludes regional nodes and adjacent organ infiltration.)

Based on Stage, Clinical Group and histology patients are now placed in different risk groups.

The following material is copied from COG educational materials.





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