RESEARCH – October 2011

Methylene blue ex vivo staining of resected colorectal cancer specimens to enhance lymph node retrieval


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Aim. Metastatic involvement of regional lymph nodes is a major prognostic factor in colorectal cancer influencing also treatment strategy. International consensus standard is retrieval of at least 12 lymph nodes from resected colorectal specimens. The aim of the present study was to assess lymph node yield and metastatic involvement of lymph nodes in colorectal specimens stained with intraarterial methylene blue.

Materials and methods. Sixty consecutive methylene blue stained colorectal specimens were analysed for lymph node count, diameter and metastatic involvement.

Results. Methylene blue staining enabled to detect 12 and more lymph nodes in 88% of the colorectal specimens with a mean number of detected lymph nodes 27.4. Metastatic lymph node involvement was detected in almost half the cases (47%). Of all lymph nodes 75% and of the metastatic lymph nodes 50% were small ( diameter ≤ 4mm). There was metastatic involvement occurred in only small lymph nodes in 18% of the N-positive patients.

Conclusions. Methylene blue staining is a simple, cheap and quick procedure enabling to retrieve 12 or more lymph nodes in the vast majority of colorectal specimens.