Abstract
Purpose::
To investigate variation of monosomy 3 status within uveal melanoma.
Methods::
17 patients with uveal melanoma that underwent primary enucleation were studied. Representative paraffin blocks were selected based on review of hematoxylin and eosin stained sections and apex and base of each tumor was demarcated. Unstained paraffin sections, 4 microns in thickness, were prepared and applied to electrostatically charged slides. After baking the slides overnight at 60o C, the sections were deparaffinized and rehydrated in organic solvents, graded alcohols, and double distilled water. Cell conditioning was preformed using Target Retrieval Solution and Proteinase K. Fluorescence in situ hybridization (FISH) was performed using directly labeled pericentromeric chromosome enumeration probes (CEP3 and CEP4) labeled with SpectrumOrange and SpectrumGreen respectively. Sections were counterstained with DAPI Antifade and scored using a Zeiss FISH workstation. Twenty nuclei in two representative fields in the preselected apex and base areas were counted; only nuclei with at least two reference CEP4 signals were counted. The CEP3/CEP4 ratio was then calculated and the Loss of CEP3/monosomy 3 was determined to be present if the CEP3/CEP4 ratio was < 0.7.
Results::
14 of the 17 samples (82%) revealed concordance of monosomy 3 (7 of 14, 50%) or of disomy 3 (7 of 14, 50%). In 3 samples (18%), there was discordance of monsomy 3 status between the tumor base (monosomy 3) and tumor apex (disomy 3). Characteristics (such as size and cell type) of 3 tumors displaying heterogeneity were similar to other tumors.
Conclusions::
Uveal melanoma displays tumor heterogeneity as evidenced by variation of monosomy 3 status within uveal melanoma. Fine needle aspiration biopsy samples obtained from the tumor base (scleral approach) and apex (tranvitreal approach) may yield disparate results.
Keywords: melanoma • genetics • uvea