ORIGINAL ARTICLE PURPOSE To evaluate accurate diagnosis and complication rates of percutaneous core needle biopsy (PCNB) with an automated gun for small lung nodules that are 10 mm or less in diameter. MATERIALS AND METHODSForty-two cases of small lung nodules with diameters ≤10 mm (mean diameter, 9 mm) that received a PCNB were included in this study. Imaging guidance was fluoroscopy in 30 cases and computed tomography (CT) in 12 cases. RESULTSAccurate diagnosis was achieved with the initial PCNB in 88.1% (37/42) of cases. Accurate diagnosis rates were 86.7% (26/30) with fluoroscopic guidance and 91.7% (11/12) with CT guidance (P > 0.05). The complication rate of PCNB was 7.1% (3/42), including hemoptysis (n=2) and pneumothorax (n=1). The complication rate was 6.7% (2/30) with fluoroscopic guidance and 8.3% (1/12) with CT guidance (P > 0.05).CONCLUSION PCNB with an automated gun is useful for the pathologically conclusive diagnosis of small lung nodules (≤10 mm in diameter) using fluoroscopic or CT guidance. Key words: • X-ray computed tomography • fluoroscopy • lung diseases • biopsyP ercutaneous core needle biopsy (PCNB) of the lung is a well-established method for the cytological diagnosis of pulmonary nodules (1, 2). PCNB is generally regarded as a safe procedure with limited morbidity and extremely rare mortality (2-5). Biopsies of pulmonary lesions as small as 3 mm in diameter have been reported (6, 7). Diagnostic accuracy rates of 90%-100% using computed tomography (CT) guidance have been documented for pulmonary lesions greater than 10 mm in diameter (3,8). For smaller lesions, however, several studies have reported decreased diagnostic accuracy in the range of 52%-88% (3, 8, 9). Moreover, no study has reported a pathologically conclusive diagnosis of PCNB for small lung nodules using CT and fluoroscopy guidance.The purpose of this study was to evaluate the accurate diagnosis and complication rates of PCNB using an automated gun for small lung nodules with diameters <10 mm. Materials and methods PatientsBetween July 2004 and October 2011, 1467 consecutive percutaneous thoracic biopsies using automated biopsy devices or fine needle aspiration were performed at our institution. Of these cases, 81 extrapulmonary thoracic lesions, such as mediastinal (n=45), chest wall (n=21), and pleural (n=13) lesions were excluded. The remaining 1386 cases of PCNB were performed on pulmonary parenchymal lesions. The enrolled population consisted of 875 males (63.1%) and 511 females (36.9%). Patients' age ranged from 8 to 88 years (mean, 66.2 years). Using axial CT scan images, the largest transverse cross-sectional diameter of each nodule was measured on picture archiving and communication system workstations. The mean diameter of each nodule was considered as its size.Of the 1386 evaluable cases, there were 52 cases of initial PCNB and 10 cases of fine needle aspiration for small nodules with diameters <10 mm. Of these cases, 42 patients receiving an initial PCNB were enrolled in this study. The enrolled group consisted...