2021 Volume 61 Issue 1 Pages 54-58
Background. Antineutrophil cytoplasmic antibodies (ANCA) are highly specific for ANCA-related vasculitis and are used to assist in its diagnosis. Although ANCA may also be present in patients with malignant tumors, few studies have reported lung cancer patients with false-positive ANCA tests. Case. A 66-year-old man was admitted to our hospital with suspected refractory pneumonia and was diagnosed with small cell lung cancer by bronchoscopy. Although his serum was positive for PR3-ANCA, no findings of vasculitis were observed, suggesting the false-positive detection of PR3-ANCA. Chemotherapy was effective against his lung cancer, and a complete remission was obtained, at which point his PR3-ANCA levels became negative. There was no recurrence of lung cancer and his PR3-ANCA level remained negative. Conclusion. Although rare, lung cancer patients may show false-positive ANCA tests results and their disease status may be evaluated according to the change in their ANCA titer.