Instrument Gauge and Type in Uveal Melanoma Fine Needle Biopsy: Implications for Diagnostic Yield and Molecular Prognostication

Abstract

To systematically evaluate and compare the effects of using small-gauge needles and vitrectors on the ability to obtain adequate diagnostic and prognostic uveal melanoma biopsy specimens. Comparative evaluation of biopsy instruments. Survival of uveal melanoma cells was evaluated invitro following needle aspiration. Five therapeutically enucleated eyes were sampled in triplicate for exvivo diagnostic biopsy experiments with 25 gauge (25 G) needle, 27 gauge (27 G) needle, and 27G vitrector. During surgery in 8 patients, paired diagnostic transscleral fine needle aspiration biopsies were performed using both 25G and 27G needles. A review of cytologic specimens was performed by a panel of 3 expert cytopathologists. A retrospective chart review was performed to evaluate 100 consecutive tumors undergoing prognostic biopsy for gene expression profiling to assess the relationship between needle gauge and prognostic adequacy. No significant cell shearing of uveal melanoma cells occurred invitro with 25 G, 27 G, or 30G needles. For exvivo biopsy samples, diagnostic yield was 100% using 25G needle (5/5) or 27G vitrector (5/5) but 60% using a 27G needle (3/5). For invivo samples, no difference in diagnostic yield was found between 25G (75%, 6/8) or 27G (75%, 6/8) needle sizes. Of 100 molecular prognostic biopsy samples evaluated, 65 were obtained using 27G needles; for these biopsies, the prognostic yield was 65/65 (100%). For diagnostic biopsy of uveal melanoma, a larger-gauge needle or a 27G vitrector may have better overall cellularity and diagnostic yield when compared to a 27G needle. However, for much more common molecular prognostic testing, a 27G needle provided adequate sample in 100% (65/65) of cases, and a larger needle provided no additional benefit.