Results of RT-PCR for SYT-SSX and β2-microglobulin products. Representative results of SYT-SSX RT-PCR are shown. Far left lane in each panel shows 100-bp molecular size standard (lowest marker represents 100 bp). Cases are designated as “SS” for synovial sarcoma and “CS” for control sarcoma. “SKW” and “SUP” are hematopoietic cell line negative controls. “Neg” is a water-only (no template) blank (primer artifact is present in A). A: SYT-SSX PCR products (expected size 101 bp). B: β2-microglobulin internal control PCR products for cases shown in A (expected size 120 bp). C: Illustration of non-specific, but similarly sized PCR products in CS cases and hematopoietic cell line controls. Note lower PCR band in CS2, CS3, CS5, SKW, and SUP sample lanes, very close to the size of positive SS case SS2. However, none of the control cases gave positive fluorescent LDR results (see Figure 3 and text). Details of cases are given in Table 2 .