A study of unilateral axillary lymphadenopathy associated with COVID-19 vaccination detected through breast cancer screening

Abstract

We investigated the frequency of development of axillary lymphadenopathy after COVID-19 vaccination in women who underwent breast cancer screening ultrasonography. All the subjects had received Pfizer’s COMIRNATY vaccine by intramuscular injection and underwent ultrasonographic examination of the breast and bilateral axillae for breast cancer screening. The ultrasonographic images were reviewed for the presence of hyperechoic areas reflecting the axillary lymph nodes, the state of the cortex, and the fat tissue in the lymph node hilum. Presence of enlarged lymph nodes was assessed by comparison with the findings on ultrasonography performed the previous year. In addition, the frequency of lymphadenopathy was examined by age and number of vaccinations. Of the total of 115 subjects enrolled in this study, 87 (76%) were found to have axillary lymphadenopathy. Hyperreactive lymphadenopathy, represented by enlargement with cortical thickening and loss of the hyperechoic hilum, was observed in 53 cases (46%). After the first vaccination, lymphadenopathy was observed in 54 (79%) of 68 subjects. The incidence of lymphadenopathy was similar across all age groups. However, the incidence of hyperreactive lymphadenopathy with cortical thickening and loss of the hyperechoic hilum tended to be higher in younger subjects. Breast cancer screening revealed a high frequency of unilateral axillary lymphadenopathy associated with COVID-19 vaccination. Guidelines are beginning to be released overseas and in Japan, regarding the timing of breast cancer screening vis-a-vis COVID-19 vaccination. It may become difficult to make the assessment if the vaccination becomes routine in the future. Before scheduling breast cancer screening, it is important to have a thorough knowledge about the development of unilateral axillary lymphadenopathy associated with COVID-19 vaccination.