Introduction/Background After the studies that demonstrate the usefulness and benefit of one-step nucleic acid amplification technique (OSNA) in sentinel lymph node biopsy (SLNB) in endometrial and cervical cancer (1–4), we wanted to evaluate the expression of cytokeratin 19 (CK19) in vulvar carcinomas in order to perform intraoperative SLNB using OSNA.

Methodology The expression of CK19 was studied in 23 paraffin tissues from vulvar biopsies diagnosed with squamous cell carcinoma from Donostia Hospital from January 2021 to December 2022. And 25 cases from Navarra Hospital from January 2021 to November 2022.

Results The total number of biopsies studied were 48. Of the 23 biopsies of Donostia Hospital, 6 were CK 19 positive (26%). However, in 25 biopsies of Navarra Hospital, CK19 positivity was observed in 10 (40%). Among positive cases, a different rate of staining was observed ( 8–95%). None of the positive cases was associated with HPV.

A relatively different rate of CK19 expression was observed between centers. One of them approaching the percentage found in another published study (5). On the other hand, the highly diverse rate found in the two hospitals also presents similarities to the difference in CK19 expression described in cervical carcinomas (5–7).

Conclusion Despite showing various positivities and in some cases of low rate, the fact of its existence makes considering the study of CK19 with immunohistochemistry in a protocol manner in biopsies of vulvar squamous cell carcinoma; patients who show such positivity could benefit from the intraoperative SLNB study with OSNA, increasing the detection of micrometastases, and avoiding the complications derived from a second intervention.

Disclosures NONE