Vaccine-induced lymphadenopathy

Case contributed by Giorgio M Baratelli
Diagnosis almost certain


A painful, visible and palpable left cervical lump of about 1.5 cm.

Patient Data

Age: 15 years
Gender: Female

A painful, visible and palpable left cervical lump of about 1.5 cm.


The ultrasound examination shows a single hypoechoic, rounded and enlarged left cervical lymph node with diffuse cortical thickening and without blood flow.

In the left axilla, multiple additional enlarged lymph nodes with uniformly thickened cortices are detected.

Normal lymph nodes are present in the right axilla and in the right cervical region.

Case Discussion

The patient received the first dose of the Moderna COVID-19 vaccine in her left upper arm 10 days prior. Vaccine-induced lymphadenopathy is an important side effect of COVID-19 vaccination.

Lymphadenopathy is ipsilateral to the injected deltoid muscle and is a clinical manifestation of an immune response.

In the Moderna clinical trials, axillary swelling or tenderness was reported in 11.6% of patients (5.0% placebo) after dose 1 and 16.0% (4.3% placebo) after dose 2 1,2.

The post-vaccination lymphadenopathy is not as common in those who received the Pfizer-BioNTech vaccine, but it was still reported among those patients.

The management of clinically evident post-vaccination lymphadenopathy is observation until the spontaneous resolution in about 4-6 weeks. Acetaminophen or ibuprofen can be used to reduce pain and inflammation.

Two key points:

  1. Lymphadenopathy as an immune response to vaccination may present a clinical diagnostic dilemma especially in persons with a history of malignancy.
  2. The Society of Breast Imaging (SBI) has recommended that women should schedule screening mammography prior to the first dose of a COVID-19 vaccination or 4-6 weeks following the second dose of a COVID-19 vaccination to prevent enlarged axillary lymph nodes caused by the vaccine being mistaken for breast cancer metastases.

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