Abstract
Purpose: :
Intraoperative transscleral fine-needle aspiration biopsy (FNAB) and fluorescent in situ hybridization (FISH) for monosomy 3 and 6p gain is an informative prognostic tool for patients with uveal melanoma. The purpose of this study was to identify melanomas that exhibit both monosomy 3 and 6p gain and to assess for heterogeneity of these aberrations among nuclei within individual samples.
Methods: :
We reviewed all cases of intraoperative FNAB in choroidal melanoma treated with iodine-125 plaque brachytherapy from July 1, 2008 to September 1, 2011, where simultaneous FISH probing of chromosomes 3 and 6p had been performed. Biopsy samples were prepared for interphase FISH according to a standard protocol, using a centromeric probe for chromosome 3 and a sub-telomeric probe specific for chromosome 6p. Hybridization signals were manually counted in 100 to 300 non-overlapping nuclei on a fluorescence microscope equipped with dual and triple bandpass filters for simultaneous visualization of the FISH signals within each nuclei. Cases that exhibited both monosomy 3 and 6p gain were included. Patients were monitored for metastatic disease.
Results: :
Of 163 patients reviewed, 14 tumors (9%) were identified with both monosomy 3 and chromosome 6p gain. The average follow-up interval was 12.5 months (range, 3.1 to 38.5 months). Of the 14 cases, 5 (36%) tumors exhibited nuclei with monosomy 3 alone or nuclei with both monosomy 3 and 6p gain. Five (36%) tumors exhibited nuclei with 6p gain alone or nuclei with both monosomy 3 and 6p gain. Finally, 4 (29%) tumors exhibited nuclei with monosomy 3 alone or nuclei with 6p gain alone. One patient in the third group has developed choroidal melanoma metastasis.
Conclusions: :
We report 14 of 163 tumors (9%) that exhibited both monosomy 3 and 6p gain by simultaneous probing via interphase FISH from FNAB. Among these cases, patients could be categorized into three subgroups based on the heterogeneity of their genetic aberrations as determined by FISH analyses. Further clinical follow-up is warranted to determine the significance of these novel findings with respect to tumor biology and metastatic prognosis.
Keywords: melanoma • fluorescent in situ hybridization • genetics