Core Biopsy and FNA: A Comparison of Diagnostic Yield in Lymph Nodes of Different Ultrasound Determined Malignant Potential

Background: The tissue diagnosis of lymphoma and metastases is commonly obtained from affected lymph nodes. The lymph nodes chosen for biopsy are often the consequence of their appearance on ultrasound, which determines their risk of malignancy. Two frequently used percutaneous sampling techniques are core biopsy and fine needle aspiration (FNA). While core biopsy obtains a larger tissue sample and provides a degree of architectural information, FNA is considered less invasive and has the advantage of immediate confirmation of adequacy by the attending cytologist. Anecdotally, core biopsy is more commonly used when a lymph node is suspected of harboring neoplasia, however a feature of malignancy is hypercellularity, which theoretically should increase the diagnostic yield of FNA. Aim: The aim of this project was to compare the diagnostic capability of FNA and core biopsy in lymph nodes of different malignant potential, as defined by ultrasound, and determine if the radiologic appearance can guide clinicians in their choice of sampling technique. The project also reviewed the role of clinical experience in both the choice of sampling technique and diagnostic yield. Methods: Retrospective study of percutaneous lymph node biopsies performed at a large tertiary hospital between July 2016 and March 2018. The associated ultrasounds were reviewed and the lymph nodes were classified as high or low risk of malignancy by their sonographic appearance. The end point for analysis was the capacity for FNA or core biopsy to provide a definitive diagnosis. The diagnostic yield was then separately assessed for lymph nodes of high and low malignant potential. The effect of clinical experience on diagnostic yield was also examined, by comparing the outcomes of radiology consultants and radiology trainees. Results: 296 lymph node biopsies were reviewed and statistical analysis was performed using logistic regression analysis. Core biopsy, in comparison with FNA, was used twice as often in lymph nodes of high malignant potential, supporting the aforementioned anecdotal evidence. Core biopsy demonstrated superior diagnostic yield in comparison with FNA, providing a diagnostic sample 45% ( P = 0.313) more often in low-risk lymph nodes and 209% ( P = < 0.05) more often in high-risk lymph nodes. Consultant radiologists used FNA 81% more often than core biopsy in lymph nodes of high malignant potential, while radiology trainees used core biopsy 104% more often than FNA in the same group. In high-risk lymph nodes, trainees were 117% ( P = 0.105) more likely to obtain a diagnostic sample than consultants. Conclusion: Core biopsy is superior to FNA in the tissue sampling of lymph nodes regardless of ultrasound determined risk of malignancy. Biopsies obtained by radiology trainees provided a diagnosis twice as often as those obtained by radiology consultants. This appeared to be the consequence of consultant preference for FNA over core biopsy.