Sentinel nodes are identifiable in formalin-fixed specimens after surgeon-performed ex vivo sentinel lymph node mapping in colorectal cancer.
BACKGROUND
In recent years, the technique of sentinel lymph node (SLN) mapping has been applied to colorectal cancer. One aim was to ultrastage patients who were deemed node negative by routine pathologic processing but who went on to develop systemic disease. Such a group may benefit from adjuvant chemotherapy.


METHODS
With fully informed consent and ethical approval, 37 patients with primary colorectal cancer and 3 patients with large adenomas were prospectively mapped. Isosulfan blue dye (1 to 2 mL) was injected around tumors within 5 to 10 minutes of resection. After gentle massage to recreate in vivo lymph flow, specimens were placed directly into formalin. During routine pathologic analysis, all nodes were bivalved, and blue-staining nodes were noted. These later underwent multilevel step sectioning with hematoxylin and eosin and cytokeratin staining.


RESULTS
SLNs were found in 39 of 40 patients (98% sensitivity), with an average of 4.1 SLNs per patient (range, 1-8). In 14 of 16 (88% specificity) patients with nodal metastases on routine reporting, SLN status was in accordance. Focused examination of SLNs identified occult tumor deposits in 6 (29%) of 21 node-negative patients. No metastatic cells were found in SLNs draining the three adenomas.


CONCLUSIONS
The ability to identify SLNs after formalin fixation increases the ease and applicability of SLN mapping in colorectal cancer. Furthermore, the sensitivity and specificity of this simple ex vivo method for establishing regional lymph node status were directly comparable to those in previously published reports.
Smith
Fraser McLean
FM
Departments of Academic Surgery and Pathology, Cork University Hospital, Wilton, Cork, Ireland.
Coffey
John Calvin
JC
Khasri
Nurul Mod
NM
Walsh
Miriam Fiona
MF
Parfrey
Nollaig
N
Gaffney
Eoin
E
Stephens
Richard
R
Kennedy
M John
MJ
Kirwan
William
W
Redmond
H Paul
HP
D000236:Adenoma / Q000473:pathology*; D015179:Colorectal Neoplasms / Q000473:pathology*; D005404:Fixatives; D005557:Formaldehyde; D006801:Humans; D009367:Neoplasm Staging / Q000379:methods*; D011446:Prospective Studies; D012394:Rosaniline Dyes; D012680:Sensitivity and Specificity; D021701:Sentinel Lymph Node Biopsy / Q000379:methods*; D013048:Specimen Handling; D016707:Tissue Fixation
D005404:Fixatives; D012394:Rosaniline Dyes; D005557:Formaldehyde; C025484:iso-sulfan blue