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case_images: a, b FDG PET-CT images of case no. 1. a Multiple enlarged left axillary and subpectoral lymph nodes measuring at least 17 mm with increased uptake SUV max 4, 12 days' post-first dose of Pfizer COVID-19 vaccine in the left arm. b Interval follow-up FDG PET-CT scan 2 months later showing complete resolution of lymphadenopathy. No other sites of metabolic active disease were identified on the scans.
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case_images: Follow-up PET-CT imaging in February 2021 revealed new FDG avid lymphadenopathy in the left axillary and subpectoral region (maximum SUV of 4) (Fig. 1a). February 2021 were due to the patient having received her first dose of Pfizer COVID-19 vaccine in the left arm 12 days prior to the scan. Follow-up PET-CT scan performed in May 2021 (Fig. 1b) showed complete resolution of all abnormal metabolic activity.
case_images: Focused ultrasound study of left axilla of patient in case no. 1 (12 days' post-first dose of Pfizer COVID-19 vaccine in the left arm) showing prominent lymph node with cortical thickening of 5 mm.
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case_images: Ultrasound of the left axilla (Fig. 2) and axillary lymph node biopsy were performed.
case_images: a-c Core biopsy of left axillary lymph node for case no. 1. a, b Hematoxylin and eosin staining showing reactive changes and focal stromal fibrosis with no evidence of metastatic carcinoma (original magnification x4 and x10, respectively). c Immunohistochemistry staining for general cytokeratin AE1/3 with no positive staining, confirming absence of metastatic carcinoma (original magnification x10). Features consistent with COVID vaccine-associated lymphadenopathy in a patient with known breast cancer.
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case_images: Histopathology revealed reactive changes and focal stromal fibrosis with no evidence of malignancy (Fig. 3a-c).
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case_images: a, b Core biopsy of left axillary lymph node, hematoxylin and eosin staining, for case 2 showing reactive lymphoid hyperplasia and no evidence of metastatic carcinoma (original magnification x4 (a) and. x10 (b)). Features consistent with COVID vaccine-associated reactive lymphadenopathy in a patient with known breast cancer.
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case_images: F4
case_images: Although the imaging was suggestive of node-positive breast cancer, core biopsy from the left axillary lymph node revealed reactive follicular hyperplasia with no evidence of malignancy (Fig. 4a, b).