[1022] The TMPRSS2-ERG Gene Fusion in Small Cell Carcinoma of the Prostate

L Xiao, Y Gong, Y Wang, P Troncoso, BA Czerniak, CC Guo. University of Texas MD Anderson Cancer Center, Houston, TX

Background: The distinction of small cell carcinoma (SCC) between prostatic and non-prostatic origins is difficult on routine histologic preparations even with the help of immunohistochemical staining. Recent studies have demonstrated that most prostate cancers carry a recurrent chromosomal translocation leading to the TMPRSS2-ERG gene fusion. Here we compared the TMPRSS2-ERG gene fusion in SCC of prostatic and non-prostatic origins.
Design: We selected 11 cases of metastatic prostatic SCC that were sampled via fine needle aspiration (FNA) and had available cell block tissue. The metastatic sites included the liver (n=10) and lymph node (n=1). Cytologic and immunohistochemical features were reviewed and the clinical information was collected from the patients' medical records. The TMPRSS2-ERG gene fusion and the copy number of the ERG gene locus were evaluated by fluorescence in situ hybridization (FISH) using the ERG gene break-apart probes. SCC of non-prostatic origins, including the urinary bladder (n=11) and the lung (n=11), also underwent the FISH analysis.
Results: The mean age of patients with prostatic SCC was 67 years (range, 54-75 years). All patients had a previous history of prostatic adenocarcinoma. The FNA specimens showed typical cytologic features of SCC. On immunostains, the tumor cells were positive for synaptophysin (9/9) and chromogranin (7/8) and negative for prostatic specific antigen (0/7). In prostatic SCC, the copy number of the ERG gene locus was increased in 6 cases, rearrangement of the ERG gene was detected in 6 cases and the rearrangement was associated with a deletion of the 5' ERG gene in 3 cases. In non-prostatic SCC, although the copy number of the ERG gene locus was increased in lung (n=8) and bladder (n=6) SCC, rearrangement of the ERG gene was not present in any of the lung and bladder SCC.
Conclusions: We studied the TMPRSS2-ERG gene fusion in SCC of prostatic and non-prostatic origins. Although the copy number of the ERG gene locus is frequently increased in SCC of both prostatic and non-prostatic origins, rearrangement of the ERG gene is present only in SCC of prostatic origin. Therefore, the TMPRSS2-ERG gene fusion is a valuable molecular marker in the distinction of SCC of prostatic origin from non-prostatic origin.
Category: Genitourinary (including renal tumors)

Monday, March 22, 2010 1:00 PM

Poster Session II # 109, Monday Afternoon

 

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