Comprehensive analysis of 112 melanocytic skin lesions demonstrates microsatellite instability in melanomas and dysplastic nevi, but not in benign nevi.
BACKGROUND
the length of DNA repetitive sequences (microsatellite instability (MSI)) represent distinct tumorigenic pathways associated with several familial and sporadic tumors.


METHODS
To investigate the prevalence and frequency of MSI in melanocytic lesions, the polymerase chain reaction (PCR)-based microsatellite assay was used to examine formalin-fixed, paraffin-embedded tissues of 30 benign melanocytic nevi, 60 melanocytic dysplastic nevi (MDN), and 22 primary vertical growth phase cutaneous malignant melanomas (CMM). Twenty-four microsatellite markers at the 1p, 2p, 3p, 4q and 9p chromosomal regions were used.


RESULTS
MSI was found at 1p and 9p in MDN and CMM but not in benign melanocytic nevi. The overall prevalence of MSI was 17/60 (28%) in MDN and 7/22 (31%) in CMM. The frequency of MSI ranged from 2/24 (9%) to 4/24 (17%) and was most commonly found at D9S162. There was a statistically significant correlation between degree of atypia and frequency of MSI (p<0.001) in MDN. There were two MSI banding patterns: band shifts and additional bands.


CONCLUSIONS
The data presented revealed the presence of low-frequency MSI (MSI-L) at the 1p and 9p regions in both MDN and CMM. Whether the MSI-L pattern reflects a defect in mismatch repair genes is still to be determined.
Hussein
M R
MR
Institute of Pathology, Case Western Reserve University and University Hospitals of Cleveland, Cleveland, Ohio, USA.
Sun
M
M
Tuthill
R J
RJ
Roggero
E
E
Monti
J A
JA
Sudilovsky
E C
EC
Wood
G S
GS
Sudilovsky
O
O
D002874:Chromosome Mapping; D004416:Dysplastic Nevus Syndrome / Q000235:genetics*; D005787:Gene Frequency; D006801:Humans; D008544:Melanocytes / Q000473:pathology*; D008545:Melanoma / Q000235:genetics*; D018895:Microsatellite Repeats; D009506:Nevus / Q000235:genetics*; D012878:Skin Neoplasms / Q000235:genetics* / Q000473:pathology*