Study Design and Sample The retrospective study included female patients who underwent breast sonography in the radiology department of Chi Mei Medical Center between July 2021 and March 2022. The patients' breast cancer history and COVID-19 vaccination history were collected and analyzed.
Analysis of Breast Sonography Lymphadenopathy is defined as an enlarged lymph node with cortical thickening \>3 mm, either concentric or eccentric, with or without effacement of fatty hilum, or in-creased non-hilar vascularity on color or power Doppler. The positive axillary lymph node findings were correlated by confirming a link to SARS-CoV-2 vaccination history within 90 days in the ipsilateral arm.
Statistical Analysis All statistical analyses were performed using the R Stats package. Descriptive summaries were reported as mean ± standard deviation for continuous variables and percentages for categorical variables. For non-parametric variables, median with interquartile range and Mann-Whitney U test were used. Statistical significance was set at a p-value \<0.05.
