Comparison of Cytopathology Yield of Fine-Needle Aspiration Biopsy Using 25G Versus 27G Needles for Melanocytic Uveal Tumors

<b>Background/Objectives</b>: This study aims to evaluate whether fine-needle aspiration biopsy (FNAB) of melanocytic uveal tumors (MUTs) using 27-gauge (27G) needles yields aspirates like those obtained using 25-gauge (25G) needles for cytology. <b>Methods</b>: A retrospective review was conducted on 32 primary uveal melanomas (PUMs). Tumors were sampled at three adjacent sites, first using a 27G needle for gene expression profile (GEP) testing, second and third with 27G and 25G needles for cytology. The endpoints evaluated were the sufficiency of aspirates for cytopathology and GEP. <b>Results</b>: Among the 32 patients, 17 tumors were choroidal, 6 ciliochoroidal, 7 iridociliochoroidal, and 2 exclusively iridic. Tumor diameter ranged from 3.3 mm to 23 mm (mean 13.2 mm), and thickness ranged from 0.5 mm to 12 mm (mean 6.4 mm). Aspirates from both needle sizes were sufficient for cytopathological diagnosis and GEP in 31 of 32 cases (96.9%). The single insufficient aspirate was insufficient with both the 27G and 25G needles. The cytopathology was identical in all other cases. The tumors were Class 1 in 22 cases (71.0%) and Class 2 in 9 cases (29.0%). <b>Conclusions</b>: FNAB aspirates of MUTs using 27G needles appear sufficient for cytology and GEP in most cases, showing a similar diagnostic yield compared to 25G needles.