Sure, that’s a meaningful percentage difference, but with the relatively small sample size and different `n` values, I don’t make much of this at the moment.
It's surprising that this type of stuff can still get published in such high journals. This just makes me think that the field of medicine is failing to grapple with its replication issues. The social sciences get more heat for bad research, but I can't imagine that this type of stuff would fly today in a remotely comparable Psychology journal.
However, to be fair to the authors, those individual numbers you point out are the quantity with lymphoma and it would be more proper to say the sample sizes were n = 1398 for the tattoo group and n = 4193 for controls. There's also nothing really wrong with having unbalanced samples here. It's either be unbalanced or throw out control data... regardless, the barely significant p-value is the biggest concern. (If you're wondering how to judge a study's robustness, the easiest and generally most effective way is to just look at the p-values).