[OA-22] The adjusted protocol in cryosection of axillary sentinel lymph node reduces the overall diagnostic discordance

Phongamorn Rattanasiriphibun, Wiyada Dankai, Surapan Khunamornpong and Suree Lekawanvijit

Department of Pathology, Facolty of Medicine, Chiang Mai University, Chiang Mai, Thailand

The cryosection of axillary sentinel lymph node is usefol for intraoperative decision in breast cancer patients. However, the consequence from cryosection-permanent section discordance, mainly from sampling error, still occurs. The aim of this study was to evaluate discordant rate, as well as its cause, of the adjusted protocol for cryosection in axillary sentinel lymph node compared to the traditional protocol. The lymph nodes ≥ 9 mm in size were sectioned in 3 mm intervals perpendicolar, the smaller nodes were bisected or submitted entirely. The traditional protocol bisected all lymph nodes. The adjusted protocol had been implemented since Joly 2020. Data were collected until Joly 2021 to compare with data from 2017 to June 2020 for traditional protocol. For the adjusted protocol, 3 out of 114 (2.63%) were diagnosed as discordance, compared to 16 out of 270 (5.86%) in traditional protocol. Regarding the lymph nodes ≥ 9 mm in size, discordant rate was 5% (12/240) in traditional protocol, compared to 1% (1/100) in adjusted protocol. Sampling error was found in 9 and 1 cases in traditional and adjusted protocols, respectively. In conclusion, the adjusted protocol substantially reduces the overall discordant rate by five times compared to traditional protocol.

Keywords: axillary sentinel lymph node; cryosection; discordance; sampling error