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Improving Diagnostic Sensitivity for Early CTCL

Initial diagnosis of cutaneous T-cell lymphoma (CTCL) is notoriously difficult to establish due to protean and often subtle clinical signs and symptoms. Histologic changes are also difficult to detect and lack reproducibility. In addition, lymphocyte immunophenotyping is no longer considered ideal for diagnosing CTCL because it lacks specificity. Polymerase chain reaction (PCR) has been used over the past several years in the detection of clonal rearrangement in T-cell populations to help identify neoplastic transformation. However, this procedure is also considered less than satisfactory and has limited sensitivity and specificity. This study evaluated a new, rapid PCR technique -- single-strand conformation polymorphism (SSCP) -- for detecting clonal rearrangement of T lymphocytes.

Researchers used SSCP and lymphocyte immunophenotyping to examine skin biopsies from 43 patients with possible CTCL. Based on the clinicopathological assessment, 26 patients had a diagnosis of CTCL and 17 patients were diagnosed as benign. The SSCP technique detected clonal rearrangements in 73% of patients with CTCL; immunophenotyping detected abnormal lymphocytes in 68% of patients with CTCL. Combining the two tests produced abnormal results in 92% of patients with a diagnosis of CTCL. The SSCP technique also detected clonal rearrangement of T lymphocytes in 12% of patients with a benign diagnosis based on the clinicopathological assessment.

Comment: Adding the SSCP analysis to PCR amplification detected a clonal population of T cells in only 73% of cases with known CTCL. This is only slightly more sensitive than previous studies using other PCR techniques that have reported detection of clonal rearrangements in 50% to 70% of patients with early stage disease, and SSCP is associated with a false-positive rate of 12%. Therefore, extreme caution must be used when interpreting the results of the SSCP method. The authors recommend using PCR-SSCP in conjunction with lymphocyte immunophenotyping studies when an early diagnosis is necessary.

— BR Smoller

Published in Journal Watch Dermatology April 1, 1999

Citation(s):

Guitart J et al. A new polymerase chain reaction-based method for the detection of T-cell clonality in patients with possible cutaneous T-cell lymphoma. Arch Dermatol 1999 135 158-162.

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