[18F]FES PET Resolves the Diagnostic Dilemma of COVID-19-Vaccine-Associated Hypermetabolic Lymphadenopathy in ER-Positive Breast Cancer.

Coronavirus disease (COVID-19) vaccination is known to cause a diagnostic dilemma due to false-positive findings on [18F]FDG PET in vaccine-associated hypermetabolic lymphadenopathy. We present two case reports of women with estrogen-receptor (ER)-positive cancer of the breast who were vaccinated for COVID-19 in the deltoid muscle. [18F]FDG positron emission tomography (PET) demonstrated primary breast cancer and multiple axillary lymph nodes with increased [18F]FDG uptake, diagnosed as vaccine-associated [18F]FDG-avid lymph nodes. Subsequent [18F]FES PET revealed single axillary lymph node metastasis in the vaccine-associated [18F]FDG-avid lymph nodes. To the best of our knowledge, this is the first study showing the usefulness of [18F]FES PET in diagnosing axillary lymph node metastasis in COVID-19-vaccinated patients harboring ER-positive breast cancer. Thus, [18F]FES PET has potential applications in the detection of true-positive metastatic lymph nodes in patients with ER-positive breast cancer regardless of the ipsilateral or contralateral side, who have received COVID-19 vaccination.

Droplets adhesion to surgical masks during standard oral surgery.

The most common routes of transmission of coronavirus disease 2019 are droplet and contact infections. During dental treatment, many instruments are used that generate droplets of saliva and blood. Several droplets are generated during extraction of an impacted third molar (M3). Surgical masks are often used during tooth extraction; however, the surface structure of surgical masks against droplets is not fully understood. Therefore, we analyzed the droplets adhered to surgical masks during impacted M3 extraction using electron microscopy. A surgical mask used during impacted M3 extraction was studied. The collected surgical mask was divided into three layers and observed using electron microscopy. The outer and inner layers had a similar mesh-like structure, while the middle layer had a denser three-dimensional structure. Droplets ranging from 20-100 µm in size generated during the extraction adhered to the fibers of the outer layer of the mask. Fewer droplets adhered in the middle layer than those in the outer layer. No droplets reached the inner layer. In conclusion, it is suggested that a surgical mask can prevent droplet infection when performing impacted M3 extraction. This study is expected to contribute to the study of infection control strategies during dental treatment in the future.