Anti-Smith Antibody Positivity Without Lupus in the Setting of Lung Cancer

The interpretation of positive serologic findings in cancer sera remains controversial. Selected antinuclear antibodies (ANAs), such as anti-double-stranded deoxyribonucleic acid (dsDNA) and anti-Smith, are highly specific for the diagnosis of systemic lupus erythematosus (SLE). On the other hand, the ANA titer is sensitive but not specific for SLE and has been reported in healthy individuals, various infections, other autoimmune diseases and cancer. We report for the first time positive anti-Smith antibody in two patients without lupus in the setting of lung cancer.