Nondiagnostic Percutaneous Transthoracic Needle Biopsy of Lung Lesions: A Multicenter Study of Malignancy Risk.

Purpose To evaluate the malignancy risk of lung lesions that show nondiagnostic results at transthoracic needle biopsy (PTNB) of the lung and to identify any malignancy-associated risk factors in each nondiagnostic category. Materials and Methods In this retrospective study, 9384 initial PTNBs (9239 patients [mean age, 65 years; age range, 20-99 years] consisting of 5729 men [mean age, 66 years; age range, 20-99 years] and 3510 women [mean age, 63 years; age range, 20-94 years]) were performed in eight institutions between January 2010 and December 2014. PTNB results were categorized as diagnostic (malignant or specifically benign) or nondiagnostic (nonspecific benign pathologic findings, atypical cells, or insufficient specimen), and the proportion of final malignant diagnoses per nondiagnostic category was obtained. Malignancy-associated factors were determined by using multivariable analyses. Results Nondiagnostic results were present in 27.6% (2590 of 9384) of PTNBs. Proportions of final malignant diagnoses were 21.3% (339 of 1592) for nonspecific benignities, 90.1% (503 of 558) for atypical cells, and 46.6% (205 of 440) for insufficient specimens. In the nonspecific benign category, granulomatous inflammation (odds ratio [OR], 0.04; 95% confidence interval [CI]: 0.02, 0.12; P < .001), abscess (OR, 0.04; 95% CI: 0.01, 0.28; P = .001), and organizing pneumonia (OR, 0.05; 95% CI: 0.01, 0.23; P < .001) were demonstrated to be important factors negating malignancy. Atypical cells suspicious for malignancy were more associated with malignancy (OR, 6.3; 95% CI: 1.9, 21.0; P = .003) than were atypical cells of indeterminate malignancy. All 130 lesions with atypical cells suggestive of malignancy were finally malignant. Conclusion After nondiagnostic lung biopsies, lesions categorized as atypical cell lesions have a high likelihood of malignancy, with somewhat lower likelihood for lesions with insufficient specimens and nonspecific benign categories. © RSNA, 2018 Online supplemental material is available for this article. See also the editorial by Elicker in this issue.