World Journal of Surgical Medical and Radiation Oncology Volume No 6

Original Article Open Access

It is Not Necessary to Examine Perinodal Fat by Histology in all Patients Undergoing Sentinel Lymph Node (SLN) Assessment by One Step Nucleic Acid Amplification (OSNA)

Lay In Lim, Mellisa Ley Hui Tan, Lisette Hammond, Mark Stephens, Sankaran Narayanan, Soni Soumian and Robert Kirby
World Journal of Surgical Medical and Radiation Oncology 2014, 3:15



NICE guidelines recommend One Step Nucleic Acid Amplification(OSNA) as an intraoperative assessment tool for the detection of sentinel node metastases in breast cancer. Fat needs to be trimmed from the sentinel node for OSNA assay. We have been assessing the excised fat histologically. The aim of this study was to analyze the results of this additional examination. Method OSNA was introduced in UHNS in 2012. Histological findings in perinodal fat analysis in patients having OSNA from November2012 to October2013 were collected and analysed utilising the pathology database.


Perinodal fat samples from 179 SLNs were analysed. 32 of 179(17.9%)SLNs were found to be positive on OSNA for macrometastases, 30 of 179(16.4%) had micrometastases and 117 out of 179 (65.4%)were OSNA negative. 95 out of 179(53%) of perinodal fat contains lymphoid tissue. Only 1 perinodal fat specimen out of 32(3.1%) OSNA positive (macrometastases) samples contained tumor cells on histology. This specimen showed a few free lying frayed tumor fragments with that were represent artefactual tumor displacement rather than genuine extracapsular tumor spread. No true extra nodal spread was identified in any specimen although extranodal spread was subsequently found in 4 out of the 32 axillary clearance specimens taken after identification of OSNA positive macrometastases. Perinodal fat from the 147 OSNA negative cases or micrometastases were all normal.


The results suggest that only perinodal fat from OSNA positive nodes should be submitted for histological examination. It is not necessary to examine fat from nodes which are negative or contain micrometastases on OSNA assessment.

Download PDF    Full Text