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

Abstract

Purpose: 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.

Design: Comparative evaluation of biopsy instruments.

Methods: Survival of uveal melanoma cells was evaluated in vitro following needle aspiration. Five therapeutically enucleated eyes were sampled in triplicate for ex vivo diagnostic biopsy experiments with 25 gauge (25 G) needle, 27 gauge (27 G) needle, and 27 G vitrector. During surgery in 8 patients, paired diagnostic transscleral fine needle aspiration biopsies were performed using both 25 G and 27 G 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.

Results: No significant cell shearing of uveal melanoma cells occurred in vitro with 25 G, 27 G, or 30 G needles. For ex vivo biopsy samples, diagnostic yield was 100% using 25 G needle (5/5) or 27 G vitrector (5/5) but 60% using a 27 G needle (3/5). For in vivo samples, no difference in diagnostic yield was found between 25 G (75%, 6/8) or 27 G (75%, 6/8) needle sizes. Of 100 molecular prognostic biopsy samples evaluated, 65 were obtained using 27 G needles; for these biopsies, the prognostic yield was 65/65 (100%).

Conclusions: For diagnostic biopsy of uveal melanoma, a larger-gauge needle or a 27 G vitrector may have better overall cellularity and diagnostic yield when compared to a 27 G needle. However, for much more common molecular prognostic testing, a 27 G needle provided adequate sample in 100% (65/65) of cases, and a larger needle provided no additional benefit.

FIGURE 1.

Cell survival of uveal melanoma cell lines following aspiration and expulsion from various small-gauge needle sizes to simulate fine needle aspiration biopsy. Smaller-gauge needles did not decrease cell viability of any of the 3 cell lines tested: Mel270 (spindle cell morphology), OM431 (epithelioid cell morphology), or OCM1 (mixed spindle and epithelioid cell morphology). Experiments were performed as 5 replicates per cell line, and viability within each cell line following passage through each needle gauge was compared to the unaspirated control and to other needle gauges using 1-way analysis of variance (ANOVA) with Tukey’s multiple comparisons. Each is expressed as a percent of the unaspirated controls, and error bars represent standard deviations. Significance was set at P < .05 and no decreases in viability were found. Mel270: 1-way ANOVA, P = .0865; Tukey’s multiple comparisons: 25 G vs 27 G, P = .9681; 25 G vs 30 G, P = .2462; 27 G vs 30 G, P = .116. OCM1: 1-way ANOVA, P = .9262; Tukey’s multiple comparisons: 25 G vs 27 G, P = .9994; 25 G vs 30 G, P = .9845; 27 G vs 30 G, P = .9953. OM431: 1-way ANOVA, P = .6982; Tukey’s multiple comparisons: 25 G vs 27 G, P = .9832; 25 G vs 30 G, P = .9997; 27 G vs 30 G, P = .9677.

FIGURE 2.

Cytopathologic evaluation of ocular melanoma aspirates. (A) Diff-Quik preparation of ex vivo fine needle aspirates performed using a 27 gauge needle, 25 gauge needle, and 27 gauge vitrector. For each gauge, 3 separate aspiration samplings were performed from different locations within each tumor (using separate needles/set-ups). (B) Hematoxylin-eosin preparation of in vivo fine needle aspirates performed using 27 gauge and 25 gauge needles. (C) Cell block preparation following 27 gauge vitrector aspiration. All images obtained at 20× magnification, scale bar 50 μm.