Small choroidal melanoma with chromosome 3 monosomy on fine-needle aspiration biopsy

Abstract

Purpose: To evaluate the presence of chromosome 3 monosomy in small choroidal melanoma using fine-needle aspiration biopsy (FNAB).

Design: Noncomparative case series.

Participants: Fifty-six patients with small choroidal melanoma measuring 3 mm or less in thickness who were undergoing plaque radiotherapy.

Methods: Fine-needle aspiration biopsy was used at the time of plaque radiotherapy to sample tumor cells using a 27-gauge long needle via an indirect transvitreal approach into the tumor apex for postequatorial tumors or a 30-gauge short needle via a direct transscleral approach into the tumor base for preequatorial tumors.

Main outcome measures: Chromosome 3 monosomy in small choroidal melanoma.

Results: The median tumor thickness was 2.6 mm. Monosomy 3 was found in 15 (27%) cases and disomy 3 was found in 32 (57%) cases. In 9 (16%) cases, genomic DNA yield was insufficient for genetic analysis. Fine-needle aspiration biopsy with a 27-gauge needle transvitreal approach provided quantity sufficient for genetic testing in 31 (97%) of 32 cases versus 16 (67%) of 24 cases sampled with a 30-gauge transscleral technique. Compared with disomy 3 tumors, monosomy 3 tumors were statistically more likely to occur in older patients (P = 0.040). Monosomy 3 (versus disomy 3) tumors showed thickness of more than 2 mm in 100% (vs. 84%), subretinal fluid in 87% (vs. 94%), symptoms in 40% (vs. 56%), orange pigment in 93% (vs. 81%), and margin of 3 mm or less to the optic disc in 20% (vs. 50%). There was no statistical difference between monosomy 3 and disomy 3 tumors in the presence or number of these clinical factors. However, small choroidal melanomas with monosomy 3 mutation were more likely to have had documented growth (63%) compared with those with disomy 3 (25%; P = 0.025; odds ratio, 5.00).

Conclusions: Using FNAB at the time of plaque radiotherapy, monosomy 3 was found in approximately 27% of small choroidal melanomas, more often in older patients and tumors with documented growth. Transvitreal biopsy into the tumor apex provided better yield compared with transscleral biopsy into the tumor base.