Fig. 5.

(Case 4): A 73-year-old female who was referred to the symptomatic breast clinic with a one-month history of a left-sided breast mass. Clinical examination revealed a 25 mm suspicious breast mass and no clinically palpable axillary or supraclavicular lymph nodes. On breast imaging, the mass was also suspicious of malignancy, measuring 26 mm on mammography and 24 mm on ultrasound scan. Axillary ultrasound at that time demonstrated no lymphadenopathy (left). The breast biopsy showed evidence of squamous cell carcinoma (SCC). Due to the unusual histology, a whole-body PET-CT scan was performed to rule out primary SCC from other sites. This did not show evidence of another primary malignancy, however, clustered left axillary and subpectoral nodes, measuring <1 cm, were identified. Those were judged as presumably inflammatory in nature, although malignant infiltration could not be excluded (middle). There was also uptake noticed within the left deltoid muscle (right). The patient had the 1st dose of the AstraZeneca COVID-19 vaccine in the left arm one day prior to the PET-CT scan. The lymphadenopathy was considered likely to be vaccine-related and the patient underwent a left mastectomy and left sentinel node biopsy, which was negative for lymph node metastasis.