Autoantibodies against CCAR1 were most frequent in anti–TIF1-γ–positive DM sera (found in 32% in both cohorts studied) and were associated with striking decreases in the odds of cancer occurring within 3 years in patients with these antibodies (OR 0.13–0.27), strongly suggesting that the combined immune response marks a subgroup in which cancer is much less likely to emerge. Here, TRIM33 is linked to dermatomyositis.