Axillary lymphadenopathy after mRNA-based COVID-19 vaccination is “not uncommon” and poses a “diagnostic dilemma” for breast cancer, according to researchers.

In a systematic review, the pooled incidence of vaccine-associated hypermetabolic lymphadenopathy detected by PET-CT was 37.3%, and the pooled incidence of clinical lymphadenopathy was 0.4%.

These findings were published in Cancer Treatment and Research Communications.


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The review included data from 10 studies. Four studies described the incidence of lymphadenopathy, and 6 studies described the clinical and imaging characteristics of vaccine-associated lymphadenopathy in the general population.

In all studies, patients received the Pfizer-BioNTech or Moderna COVID-19 vaccines. In 1 study, some patients received the Oxford-AstraZeneca vaccine as well.

The pooled incidence of clinical lymphadenopathy after vaccination was 0.4% (range, 0.3%-3.4%), and the pooled incidence of vaccine-associated hypermetabolic lymphadenopathy detected by PET-CT was 37.3% (range, 34.9%-53.6%).

The pooled mean time from vaccination to axillary lymphadenopathy was 6.9 days (range, 2-18 days). The pooled mean maximal node diameter was 18.2 mm (range, 16-21 mm).  

The researchers highlighted that the timing of lymphadenopathy is important for determining whether additional testing is necessary.

Lymphadenopathy that is detected less than 6 weeks after vaccination is of low suspicion and is recommended to be followed by surveillance. Lymphadenopathy detected 6 weeks or later after vaccination is of higher suspicion, and additional workup may be necessary.

Based on their findings, the researchers concluded that “proper arrangement of vaccination and imaging regarding timing and laterality should be advocated to avoid confusion and patient anxiety.”

Reference

Co M, Wong PCP, Kwong A. Covid-19 vaccine associated axillary lymphadenopathy – A systematic review. Cancer Treat Res Comm. Published online 11 March 2022. doi:10.1016/j.ctarc.2022.100546