Original Article

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, ^*Robert Kirby

General Surgery, University Hospital Of North Staffordshire, Stoke-On-Trent, United Kingdom

• Submitted Friday, September 19, 2014
• Accepted:Tuesday, October 21, 2014
• Published Thursday, October 23, 2014

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited

Abstract

Introduction

Results

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.

Conclusion

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.

Introduction

Most units proceed to axillary clearance following a diagnosis of positive axillary nodes found at Sentinel Lymph Node Biopsy. Intra operative assessment of sentinel lymph nodes (SLNs) allows a decision to be made for immediate conversion to axillary clearance at the time of initial surgery for breast cancer. This avoids the need for re-admission at a later date and allows adjuvant treatment to start earlier. In August 2013, NICE recommended One Step Nucleic Acid Amplification (OSNA) to be used intra-operatively for the detection of SLN metastases [1]. OSNA is a new technology which is used to measure cytokeratin19 (CK19) mRNA by loop mediated isothermal amplification. CK19 is an epithelial marker which is expressed in most breast cancers but is not normally present in healthy lymph node tissue [1 2]. OSNA gives a quantitative analysis of the number of mRNA copies and this score determines whether the SLN is negative for metastases or contains micro metastases, macro metastases and therefore whether the patient requires axillary clearance.

As part of the process of preparation for OSNA assay, perinodal fat needs to be trimmed from the SLN to facilitate accurate assessment. Although this fat can simply be discarded, there is always a lingering uncertainty that vital histological information might be lost. The perinodal fat trimmed can have shavings of nodal tissue included that might harbour tumour, another reason to examine it is it might contain extranodal spread. The value of separate histological perinodal fat assessment in the identification of extra-nodal metastatic disease in this situation has not yet been determined. OSNA was introduced in UHNS in November 2012. The aim of this study was firstly to assess the incidence of positive histological findings in perinodal fat in patients having SLN assessment by OSNA, and secondly to determine the value of carrying out routine perinodal fat assessment when OSNA has shown SLNs to be involved by tumour or when normal.

Patients and Methods

A prospective examination was carried out of all perinodal fat samples taken from SLNs during the 12 months between November 2012 and October 2013. Data were collected using a standardised audit form and histology results were obtained from the pathology database.

Results

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 tumour cells on histology. This specimen only showed a few free lying frayed tumour fragments with that were represent artefactual tumour displacement rather than genuine extracapsular tumour 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. The perinodal fat from the 147 OSNA negative cases or micrometastases were all normal.

Discussion

The processing of perinodal fat necessitates time and expense for a pathology laboratory. This study has shown that this time and expense did not result in additional information affecting management in any of the studied patients. The complete absence of any tumour in the perinodal fat of negative SLNs would suggest that routine assessment of such specimens is not worthwhile. . The identification of presence of tumour cell in the perinodal fat in one positive node suggests that such findings are possible, especially where subsequent extranodal spread has been demonstrated in 4 cases following axillary nodes clearance. This could affect treatment decisions in the absence of other pathologically identifiable disease.

There are differing opinions regarding the significance of extranodal spread of tumour within the axilla and what should be done when it is identified. Although some studies demonstrate a reduction in survival rate in patients with extranodal spread this situation is not commonly associated with axillary relapses [3 4]. Bucci et al., suggest that extranodal spread in axillary lymph node does not warrant axillary radiation [3]. Fisher et al, however, recommend breast/chest wall and supraclavicular radiation for all patients with pathologic evidence of such extranodal extension who have had a level I and II axillary dissection regardless of the number of positive axillary nodes [4]. As there is no clear consensus on this, different units have their own guidelines. Therapeutic decisions following diagnosis of extracapsular spread remain a matter of debate.

Conclusion

It is not necessary for SLN perinodal fat to be submitted routinely for histology following OSNA assessment. A selective approach should be taken. One of 32 (3.1%) OSNA positive cases had identifiable tumour in peri-nodal fat after SLN excision. None of the OSNA negative cases had positive peri-nodal fat histology. We suggest that peri-nodal fat should not be submitted for histology when OSNA assessment of the SLN has shown it to be negative. Only peri-nodal fat from OSNA positive nodes should be submitted for histological examination. It is possible that perinodal fat assessment will not be necessary for SLNs found to contain only micrometastases on OSNA.

Authors Contributions

LIL-collected data, analyzed data, written up the article
MLHT-assisted to analyze data, review of article
LH-contribution of data-histology report, review of article
MS-contribution of data-histology report
SN-review of article
SS-contribution of idea, review of article
RK-contribution of idea, review of article

Conflict of Interests

The authors declare that there are no conflicts of interests

Ethical Considerations

The study was approved by the institute ethics committee.

Acknowledgement

None

Funding

None declared

References

[1].Nice guidance August 2013. Intraoperative tests (RD-100i OSNA system and Metasin test) for detecting sentinel lymph node metastases in breast cancer. Nice diagnostic guidance8.http://www.nice.org.uk/guidance/DG8 [Last accessed October 22, 2014]http://www.nice.org.uk/guidance/dg8/resources/guidance-intraoperative-tests-rd100i-osna-system-and-metasin-test-for-detecting-sentinel-lymph-node-metastases-in-breast-cancer-pdf

[2].Pegolo E1, Puppin C, Gerometta A, Damante G, Puglisi F, Di Loreto C. One-step nucleic acid amplification (OSNA) for intraoperative evaluation of sentinel lymph node status in breast cancer: a comparative study between CK19 protein expression and CK19 mRNA level in primary tumors and lymph node metastasis. Virchows Arch. 2013 Jul;463(1):7-15. doi: 10.1007/s00428-013-1440-2. Epub 2013 Jun 19. [Pubmed]

[3].Bucci JA, Kennedy CW, Burns J, et al. Implications of extranodal spread in node positive breast cancer: a review of survival and local recurrence. 49th Annual Scientific Meeting of the Royal Australasian College of Radiologists, October 1998, Brisbane, Queensland.

[4].Fisher BJ1, Perera FE, Cooke AL, Opeitum A, Dar AR, Venkatesan VM, Stitt L, Radwan JS. Extracapsular axillary node extension in patients receiving adjuvant systemic therapy: an indication for radiotherapy? Int J Radiat Oncol Biol Phys. 1997 Jun 1;38(3):551-9. [Pubmed]