COVID Vaccination Findings on Mammography

IMAGING FINDINGS: ​
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Standard Mediolateral Oblique (MLO) views demonstrate an asymmetrically enlarged lymph node in the left axilla. No abnormality is identified in either breast.  Sonographic evaluation of the left axilla demonstrates an abnormal enlarged lymph node with a thickened cortex. The patient reports that she had a COVID vaccination in the left arm two weeks ago.  
 
WHY IT MATTERS:

1. There is hope in the COVID19 global pandemic as vaccines are being deployed. Vaccinations can cause temporary unilateral axillary lymphadenopathy. This is seen commonly after administration of the COVID19 and Shingles vaccines. The majority of patients with a recent vaccination will show some degree of axillary node enlargement on the side of vaccination. This typically resolves within several weeks.
2. Short-term follow-up of these patients is likely not required if the story fits, especially as the vaccine becomes more wide-spread. Reactive lymphadenopathy due to other causes is often followed until the nodes return to normal size. But given the prevalence of mild left axillary lymphadenopathy with a recent left arm vaccination site = we recommend to simply continue with regular screening. Please note, that some practices are recommending short-term follow-up, however at a busy practice in an area where COVID vaccination is occurring, this could be dozens of patients per day. Another approach for unilateral axillary lymphadenopathy with recent history of COVID vaccination and a normal screening mammogram is to perform screening ultrasound for those with dense tissue (to help ensure no occult malignancy), but otherwise return to routine screening.

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FURTHER READING:
Unilateral axillary Adenopathy in the setting of COVID-19 vaccine  (Elsevier 2021)