Utility of flow cytometry and gene rearrangement analysis in tissue and blood of patients with suspected cutaneous T-cell lymphoma

Cutaneous T-cell lymphoma (CTCL) is difficult to diagnose at an early stage. Current diagnostic tools include clinical examination, histomorphologic analysis, immunohistochemistry, flow cytometry of peripheral blood and/or lesional tissue, and evaluation of T-cell receptor (TCR) clonality by gene rearrangement analysis (TCRGR). Advances in genomic sequencing, including high-throughput sequencing (HTS), can be used to identify specific clones of rearranged TCR genes. Even with all of these tools, CTCL can take as long as a decade to definitively diagnose, potentially delaying treatment options and causing patient anxiety. This study aimed to evaluate the performance of the various ancillary testing modalities used to diagnose early-stage CTCL. In a subset of patients the performance of HTS was compared to flow cytometry and conventional TCRGR analysis via polymerase chain reaction (PCR). Fifty-five patients, with a total of 68 skin biopsies and peripheral blood draws, were evaluated using flow cytometry, PCR-TCRGR, and HTS-TCRGR to determine the sensitivity and specificity of each ancillary test. In tissue biopsies, flow cytometry (64%), PCR (71%) and HTS (69%) shared similar sensitivities; flow cytometry had the highest specificity (93%), followed by HTS (86%) and PCR (76.9%). However, flow cytometry and PCR had insufficient DNA quantities in 29 and 15% of the specimens, respectively. Peripheral blood testing was less sensitive than tissue testing (flow cytometry 14%, PCR 41%, HTS 33%); in peripheral blood, HTS was the most specific test (flow cytometry, 70%; PCR, 62.5%; and HTS, 100%). HTS is a highly specific molecular test for identifying CTCL in peripheral blood and skin biopsy specimens; however, our findings suggest a need for a continued search for more sensitive tests for early-stage CTCL.

Automated summary

Cutaneous T-cell lymphoma (CTCL) is challenging to diagnose early, with diagnostic tools including clinical examination, histomorphologic analysis, immunohistochemistry, flow cytometry, and gene rearrangement analysis. A study compared the performance of different diagnostic modalities, with high-throughput sequencing (HTS) showing high specificity in identifying CTCL. Further research is needed to find more sensitive tests for early-stage CTCL.