Q&A column, 4/15

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Editor: Frederick L. Kiechle, MD, PhD

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Lymph node retrieval in colon cancer

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Q. Why is the number 12 for lymph node retrieval in colon cancer protocol reporting not specific to the kind of resected specimens and whether a total colectomy was performed?

A. It is important to realize that the number 12 is not a magic number, and other cutoffs and parameters, like lymph node ratio, have been proposed as better prognostic indicators.1–3 The idea of a cutoff is based on data that show that cases designated as stage II based on examination of fewer than 12 lymph nodes have worse outcomes than stage II cases based on examination of 12 or more lymph nodes.3,4 At the practical level, it means the following:

• If fewer than 12 lymph nodes are retrieved, a more extensive search should be done, perhaps with acetone or other fat-clearing solutions.5
• The search for lymph nodes should not stop once 12 lymph nodes have been obtained, but special techniques such as acetone are perhaps not warranted once this number is achieved.
• It is well known that specimens from the rectosigmoid region and those obtained after neoadjuvant therapy typically have fewer lymph nodes.6 If 12 lymph nodes are not obtained in these cases even after acetone treatment, the standard of care (from the pathology side) has been met.

I personally do not like the idea of having different cutoffs for different situations. Having one cutoff is one too many. If the limitations of certain kinds of specimens are taken into account and acetone treatment is done, the cutoff of 12 is fine for all situations. The utility of this cutoff at a practical level is to ensure a thorough search for lymph nodes. It is not a threshold to be used as a mark of failure or inferior work ethic, if a thorough search has been performed.