Dermatofibrosarcoma protuberans (DFSP) is a dermal and subcutaneous
tumor of intermediate
malignancy. The most remarkable cytogenetic feature of DFSP is the
chromosomal translocation t(17;22)(q22;q13), causing a fusion of the
platelet-derived growth factor beta chain (PDGFB) gene at 22q13, and the
collagen type 1 alpha 1 (COL1A1) at 17q22. The aim of the study was to analyze the molecular characteristic of DFSP in conjunction with histopathological and clinical features. We performed fluorescence in situ hybridization (FISH) and multiplex
reverse transcriptase-polymerase chain reaction (RT-PCR) to detect
chromosomal translocations and fusion gene transcripts in 16
formalin-fixed,
paraffin-embedded DFSP samples. In addition, the amplification of
PDGFB was also evaluated in the 16 DFSP samples by real-time PCR. FISH analysis revealed that all the 16 samples exhibited COL1A1-PDGFB gene fusion. Eleven out of 11 informative cases (100%) showed fusion transcripts by multiplex RT-PCR analysis. Various exons of the COL1A1 gene were fused with the PDGFB gene. Among them, exon 25 was found to be more frequently involved. Real-time PCR showed that the
PDGFB copy number increase in the DFSP samples was higher than in normal skin tissues (p=0.007). Values of FISH fusion signals and
PDGFB DNA analysis were variable between samples, but suggested that increased values might be associated with parameters of
tumor progression. Our results confirm that analysis of the COL1A1-PDGFB status by FISH and RT-PCR is a useful tool in the confirmation of a DFSP diagnosis. In addition, the analysis of
PDGFB copy number status may become a useful diagnostic marker since the gene is a potential target for treatment of DFSP patients.