Abstract
Abstract: :
Purpose: Cytogenetic analyses of uveal melanomas have identified several non-random alterations that appear to correlate with prognosis. Specifically loss of an entire chromosome 3 homologue (monosomy 3) shows a significant correlation with metastasis and decreased survival and appears to be a better prognostic indicator than selected clinical and histopathological criteria at least in the short term. To date, the majority of these studies have utilised fresh tissue or chromosomes extracted from tissue sections. The aim of this study was to develop a technique to identify monosomy 3 in tissue sections using chromosome in situ hybridization (CISH). Methods: In situ hybridization for centromere-specific probes to chromosome 3 and 18 was performed on 10 archival paraffin embedded choroidal melanomas. In all 10 cases the patients had died from metastatic disease. The number of copies of chromosome 3 within the tumour was compared with that in surrounding normal tissues and with in situ hybridization for chromosome 18,which does not appear to be involved in the pathogenesis of uveal melanoma. Results: In situ hybridization for chromosome 3 and 18 was carried out successfully on 10 choroidal melanomas. Based on the chromosome index (number of hybridization sites counted divided by the total number of nuclei counted) and signal distribution (percentage of nuclei with 1, 2 or more hybridization sites), 9 tumours were defined as monosomic and one case was balanced for chromosome 3. All ten cases were balanced for chromosome 18. Conclusions:CISH is a relatively inexpensive and easy technique that can be successfully applied to archival paraffin embedded choroidal melanomas. This will allow detailed study of a large archival series and comparison with histopathological parameters and clinical outcome. Furthermore, if adjuvant treatment becomes available, this technique could be used to identify patients at risk from metastases who would benefit from such therapy at the time of initial diagnosis.
Keywords: melanoma • pathology: experimental • in situ hybridization