Abstract
Purpose: :
To assess improvement in detection of monosomy 3 in patients with uveal melanoma using fluorescence in situ hybridization (FISH) with both centromeric (CEP3) and 3p25 probes.
Methods: :
Consecutive cases of uveal melanoma treated by enucleation from 2004 to 2010 at the Cole Eye Institute were analyzed. Genomic DNA was isolated from fresh frozen tumor tissue and amplified by PCR. Tumors were analyzed for monosomy 3 using single nucleotide polymorphism array (SNP-A) (Illumina, San Diego, CA). For comparison, FISH analysis was performed using both a chromosome enumeration probe (CEP3) and a probe for 3p25 (Abbott Molecular, Des Plains, IL). A total of 200 interphase cells were scored to determine the percentage of signals.
Results: :
Tumors from 49 Caucasian patients with uveal melanoma were analyzed. Patients included 28 males (57%) and 21 females (43%). The average age at diagnosis was 64 years. Tumor location was choroidal in 24 (49%), ciliochoroidal in 17 (35%), and iridociliochoroidal in 8 cases (16%). SNP-A detected monosomy 3 in 31 tumors (63%). SNP-A further identified partial chromosomal gains and losses in 6 cases (12%). These included partial loss of 3p (n=3), partial loss of 3q (n=2), and partial gain of 3q (n=1). Statistical analysis identified a cut-point of 20% as yielding optimal sensitivity and specificity for determining monosomy 3 in tumors analyzed by FISH. Of tumors with monosomy 3 identified by SNP-A (n=31), FISH CEP3 detected 24 (77%). FISH using the 3p25 probe detected 28 tumors (90%), including every case that was detected by FISH CEP3. The sensitivity of FISH CEP3 was 77%. When the 3p25 probe was used, the sensitivity increased to 90%. In our series, 17 patients (35%) currently have metastatic disease. Of these, monosomy 3 was detected by SNP-A in 16 cases (94%), by FISH CEP3 in 10 cases (59%), and by the 3p25 probe in 12 cases (71%).
Conclusions: :
FISH analysis using a 3p25 probe improves the detection of monosomy 3 in patients with uveal melanoma by approximately 17% compared to a centromeric probe alone. In the future, new FISH probes could be generated based upon SNP-A data thereby increasing sensitivity for detection of high risk tumors.
Keywords: melanoma • genetics • fluorescent in situ hybridization