Sentinel lymph node biopsy in rats. Comparison between paraffin and frozen section analysis

PURPOSE:To simulate a lymph node metastasis in an animal model using activated carbon, assess their identification in frozen section analysis and compare with histopathological examination in paraffin.METHODS:Thirty two adult female rats were used. They received the carbon injection on its hind legs. Half of the rats was sacrificed on day one, and the other half after 21 days. Thus, 64 lymph nodes were dissected and split longitudinally. One half of the lymph node was sent immediately to frozen section analysis. The other half was fixed in 10% formaldehyde to be cut in paraffin. Slides were divided into quadrants and classified by the presence of carbon in these four quadrants_ They were also classified by the carbon staining intensity.RESULTS:Comparing the slides obtained in the first day and 21 days, there was a tendency of carbon to spread over time, but without statistical significance. The intensity did not alter over time.CONCLUSION:There was no concordance between the two methods of pathological analysis, however the actived carbon was seen in all lymph nodes.UNIFESPUNIFESP Pathology DepartmentUniversidade Federal de São Paulo (UNIFESP) Department of SurgeryUNIFESP, Pathology DepartmentUNIFESP, Department of SurgerySciEL