Ex vivo sentinel lymph node study for rectal adenocarcinoma: preliminary study

Area of Science:

• Oncology
• Surgical Pathology

Background:

• Sentinel lymph node (SLN) detection is established for colon cancer but not extensively studied for rectal cancer.
• Ex vivo techniques are currently the primary method for SLN assessment in rectal cancer.

Purpose of the Study:

• To evaluate the feasibility and impact of ex vivo sentinel lymph node detection using blue dye injection in patients with rectal adenocarcinoma.

Main Methods:

• A prospective study involving 31 patients with rectal adenocarcinoma undergoing proctectomy.
• Submucosal peritumoral blue dye injections were administered, followed by ex vivo examination of the surgical specimen.
• Sentinel lymph nodes were sectioned at three levels and analyzed using hematoxylin-eosin (H&E) staining and immunohistochemistry (IHC).

Main Results:

• A sentinel lymph node was identified in 97% of cases (30 out of 31 patients), with a mean of 2 SLNs retrieved per patient.
• Micrometastases were detected in 3 of 23 initially node-negative (pN0) cases upon detailed histological examination of SLNs, leading to upstaging to pN1.
• The false-negative rate for SLN detection was 43% in patients with confirmed positive lymph nodes (N+).

Conclusions:

• Ex vivo sentinel lymph node detection is a feasible and simple technique for rectal cancer.
• Hematoxylin-eosin staining remains the gold standard for histopathological analysis.
• SLN detection can significantly impact tumor staging, potentially upstaging approximately 15% of T2-3N0 rectal cancers to T2-3N+.