Depletion of Core Needle Biopsy Cellularity and DNA Content as a Result of Vigorous Touch Preparations

Abstract

Context Touch preparations (TP) of core needle biopsies (CNBs) are used at some institutions for on-site assessment of CNB adequacy. In our clinical practice, we have encountered instances in which TPs resulted in substantial depletion of CNB cellularity. Objective To examine the effect of increasingly vigorous TPs on cellularity and DNA content of CNBs. Design Ex vivo CNBs (n = 56) were performed on resected lung and kidney tumor specimens. For each specimen, CNBs were performed in quadruplicate on tumor and nontumor tissue and subjected to 1 of 4 TP methods: imprint, 1-cm drag, 2-cm drag, or full-slide drag. Overall cellularity in TPs relative to corresponding CNBs was estimated semiquantitatively. DNA was extracted and quantified from 12 TPs and corresponding CNBs. Two cytopathologists performed a blinded diagnostic assessment of Diff-Quik–stained TPs. Results Cellularity of imprint, 1-cm, 2-cm, and full-slide TPs represented, on average, 19%, 33%, 41%, and 46% of total CNB cellularity, respectively (p = .003). Average DNA content in imprint, 1-cm, and 2-cm TPs was 0.3 μg (range, 0.1–0.8 μg), 0.4 μg (range, 0.1–1 μg), and 0.6 μg (range, 0.2–1.3 μg), respectively, which represented on average 15%, 36%, and 50%, respectively, of total CNB DNA content. Diagnostic accuracy was not inferior for less-extensive TPs, compared with more-extensive TPs. Conclusions Vigorous TPs may contain a substantial fraction of CNB cellularity and DNA content, whereas more-limited TPs are less disruptive to CNBs but remain suitable for cytologic assessment. We suggest avoiding excessively forceful TPs and, whenever clinically feasible, obtaining additional samples to ensure sufficient cellularity for potential ancillary studies.