Sentinel node mapping in colon carcinoma: in-vivo versus ex-vivo approach

The aim of this study was to determine if ex-vivo and in-vivo technique of lymphatic mapping for colorectal cancer (CCR) result in similar sentinel lymph node (SLN) identification and accuracy rates.

Thirty consecutive patients with 32 CCR underwent in vivo SLN mapping. After completion of the colectomy, we remapped the SLN in the operative specimens from patients who had undergone successful in vivo lymphatic mapping.

At least one SLN was identified by in vivo approach in 32 tumours. 1.5 SLNs (1-3) and 1.8 SLNs (1-4) (p=0.24) were identified by the in vivo and the ex vivo technique, respectively. All SLNs identified by the in vivo technique were also identified by the ex vivo technique. In six cases one and in two cases two additional SLNs were identified with the ex vivo technique. Twelve percent of tumours were upstaged.

Ex vivo SLN mapping is as accurate as the in vivo technique in defining SLN and does have the ability to upstage some patients with CCR. The ex vivo technique could be used either as a primary lymphatic mapping procedure or secondarily for failed in vivo attempts at lymphatic mapping.