US-guided biopsy for lung cancer diagnostics: are core biopsies superior to FNA?

<bold>Background:</bold> percutaneous biopsies are low-cost, safe procedures with key role in diagnosis of lung cancer. With the need for more tissue for extensive testing panels, are core biopsies (CB) superior to fine needle aspiration(FNA)? <bold>Methods:</bold> Patients having US-guided biopsies for suspected thoracic cancer between 2022-23 were included. Procedure were done by radiologists & pulmonologists. Biopsies included lung masses, pleural nodules, neck & axillary nodes. Where feasible both FNA using 21G needle followed by 16-18G tru-cut needles CB were done. Samples were sent separately to pathology for initial analysis including IHC followed by ancillary testing (e.g. PDL-1 expression, mutations). Where indicated, adenocarcinoma case were sent to whole genome sequencing (WGS). Data on adequacy of biopsies for different levels of testing were collected. <bold>Results:</bold> 46 cases were included. FNA & CB were both done in 24 cases; CB only done 14 & FNA only in 8. The diagnostic yield for IHC was 41/46 (89%). The final diagnosis was small cell lung cancer in 7, non-small cell lung cancer in 29 (20 adeno, 5 squamous, 4 NSCLC-NOS), mesothelioma in 3, & extrathoracic cancer in 2. For IHC, FNA was diagnostic in 26/32 (81%), CB was diagnostic in 34/38 (89%). For ancillary testing, FNA was diagnostic in 9/14 (64%) & CB diagnostic in 8/12 (67%). Regarding WGS, FNA was sufficient in 6/8 (75%) and CB sufficient in 7/11 (64%). In 14 cases where WGS was indicated and CB & FNA samples were available, FNA samples were chosen for WGS in 6 cases (43%), & CB in 8 (57%) cases. <bold>Conclusion:</bold> In the era of sequential testing for lung cancer, FNA & CB are complimentary. None is overtly superior & both modalities should be considered where feasible.