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Sentinel lymph node (SLN) biopsy is a widely used staging procedure. As recently reviewed, possible problems with microscopic interpretation include false positive immunohistochemical staining and benign lesions mimicking metastasis.1 To my knowledge, no histological artefacts, especially no lymphangiography artefacts, have been attributed to this procedure. I recently encountered an artefact that at first glance seemed to be a lymphangiography artefact.
SLN biopsy is used in our hospital for the staging of breast cancer and was introduced in July 2001. The details of our procedure are as follows. The radioactive tracer is injected intracutaneously or subcutaneously in the affected quadrant of the breast 24 hours before surgery. On the morning of the operation, patent blue dye is injected intracutaneously or subcutaneously in the affected quadrant of the breast. SLN biopsies are fixed in formalin and stored in the operating theatre for 24 hours, after which time, the amount of radioactivity is low enough for the specimens to be transported by public highway with no special measures or a licence.
In March 2003, we received two SLN biopsies on the same day, both with artefacts. Throughout the lymph nodes there were empty holes with no reactive changes (fig 1). A similar artefact was noted in the tumour of one of the lumpectomy specimens, making grading of this tumour impossible. All tissues seemed to be adequately fixed in formalin and paraffin wax embedded. No artefacts were noted in other specimens that were processed on the same day. A link was made with the SLN procedure and the artefacts were interpreted as possible lymphangiography artefacts. The departments of surgery and nuclear medicine were contacted to ask whether there had been any changes in the SLN procedure. Both of these departments denied changes to their procedures; specifically, neither of the two tracers was injected in or near the tumour and there was no change in the composition of the tracers. The SLNs taken in 2002 were reviewed and it was noted that the first SLN with the same artefact was taken in the last week of December and the same artefact was also seen in SLNs from January and February 2003. However, the lymph nodes were assessed by different pathologists and the artefacts were not interpreted as related to the SLN procedure.
The department of surgery was again contacted and one of the nurses from the operating theatre mentioned that the SLN biopsies were stored in a refrigerator until transportation. This refrigerator had been switched on after reorganisation of the operating theatre in December 2002, but before that date it had been switched off. On several occasions she had noticed that tissues stored in the refrigerator were frozen and for this reason the refrigerator had been serviced twice, although no improvement was seen. This problem had not been reported to our laboratory and we had never noticed that the SLN specimens were frozen on arrival. We concluded that the artefacts in the SLNs were freezing artefacts and the refrigerator was switched off. Since then the artefact has disappeared.