Gastrointestinal Tract
Maximizing Lymph Node Yield
Austpath SOP for Lymph Node Dissection
Our SOP (standard operating procedure) for colorectal cancer resections involves a meticulous two-step process:
-
Initial Dissection: Upon receiving the specimen, an operator carefully dissects the pericolic/perirectal fat to identify visible lymph nodes.
-
Formalin Fixation: The specimen is fixed in formalin for 24 hours, allowing the tissue to firm up, which enhances the ability to detect additional lymph nodes.
-
Re-Dissection: A second, independent operator then re-dissects the specimen after formalin fixation, meticulously searching for any remaining lymph nodes.
In our laboratory this rigorous approach typically yields, on average, 6 additional lymph nodes, reflecting the effectiveness of our procedure.
Why is this important?
Studies show that a higher number of lymph nodes harvested during surgery is directly linked to better overall survival (OS), particularly in patients with stage II and III colorectal cancer.
Does the Number of Lymph Nodes Change the Tumour's Behaviour?
No.
The survival benefit from harvesting more lymph nodes is due to more accurate staging, rather than directly improving cancer biology. This concept, known as stage migration or the "Will Rogers phenomenon", suggests that by identifying more metastatic lymph nodes through thorough dissection, some patients who might have been classified as stage II are correctly upstaged to stage III. This shift in classification allows for more appropriate treatment, such as adjuvant chemotherapy, which improves survival outcomes without altering the cancer's intrinsic behaviour.
Conclusion
While a higher lymph node yield reflects the quality of surgical and pathological care, it does not directly affect the biology of the tumour. Instead, the benefit lies in more accurate staging, which guides more effective treatment plans and leads to better survival outcomes for patients.