Introduction/Background*In cervical cancer, the sentinel lymph nodes (SLNs) are processed according to the pathological ultrastaging protocol. As part of this protocol immunohistochemistry with cytokeratin AE1/AE3 is performed in addition to standard hematoxylin and eosin (H&E) staining, aiding the detection of low volume disease (i.e. micrometastases and isolated tumour cells (ITC)). Current guidelines advise routine use of cytokeratin immunohistochemistry. We studied the pathological yield, in terms of detecting low volume disease, and cost-effectiveness of this routine immunohistochemistry use.

Methodology We retrospectively included all FIGO stage IA-IIA1 cervical cancer patients who had undergone SLN procedures at our institution between 2007 and 2020. Pathological data were collected from every patient including the number of SLNs stained with cytokeratin imunohistochemistry. Data were analysed using descriptive statistics and McNemar test.

Result(s)*In total 232 cervical cancer patients had undergone a successful SLN procedure harvesting a total of 647 SLNs. Of these nodes, 540 SLNs from 215 patients were routinely processed with cytokeratin immunohistochemistry. Immunohistochemistry identified low volume disease in 25 SLNs from 22 patients: 14 with micrometastases (11 patients) and 11 with ITC (11 patients). Four nodes with micrometastases (three patients) and six nodes with ITC (six patients) would have been missed without the routine use of immunohistochemistry. Overall, 54 SLNs needed to be immunohistochemically stained to detect one additional SLN with low volume disease, 135 for micrometastases and 90 for ITC, leading to an expenditure of €5920 to identify one additional low volume diseased SLN: €14800 for micrometastases and €9867 for ITC. Compared to H&E staining, routine immunohistochemistry significantly increased the rate of patients with low volume disease from 18 (8.4%) to 26 patients (12.1%) (p=0.02). When only micrometastases were considered as tumour positive, routine immunohistochemistry increased the rate of patients with positive sentinel lymph nodes from 12 (5.6%) to 15 patients (7.0%) (p=0.25).

Conclusion*The routine use of cytokeratin immunohistochemistry improves the detection of low volume disease in early-stage cervical cancer, though predominantly ITC, but is expensive.