Improved sensitivity of T-cell clonality detection in mycosis fungoides by hand microdissection and heteroduplex analysis

Background: The presence of a dominant T-cell clone is an important diagnostic criterion in cutaneous T-cell lymphomas (CTCLs) and in atypical T-cell cutaneous infiltrates. Procedures based on polymerase chain reaction (PCR) are the most sensitive to detect clonality, but heteroduplex analysis is less sensitive than other methods such as denaturing gradient gel electrophoresis. Objective: To assess whether a gross hand microdissection of the superficial (papillary) portion of the dermal infiltrate may improve the sensitivity of T-cell clonality detection by PCR-heteroduplex analysis in CTCL. Setting: Regional university hospital (secondary or tertiary referral center). Patients: A total of 29 patients with a definite diagnosis of mycosis fungoides based on typical histologic and immunophenotypic features were selected with patch (16) or plaque (13) stages. Main Outcome Measures: Assessment of T-cell clonality by PCR amplification of the T-cell receptor gamma chain followed by heteroduplex analysis using DNA extracted from the entire biopsy specimen and after gross microdissection of the subepidermal bandlike dermal infiltrate. Results: T-cell clonality was demonstrated in 24 of 29 cases when hand microdissection was used compared with 16 of 29 cases with DNA analysis from entire biopsy specimens; thus, hand microdissection resulted in a sensitivity improvement of approximatively 50%. Conclusions: Hand microdissection substantially improves the detection of a T-cell clone in CTCL when using a PCR-heteroduplex analysis and could be used routinely in the clinical evaluation of T-cell infiltrates. Importantly, the microdissection method was found to be more useful for the detection of T-cell clones in early patch stages of CTCL than in plaque-stage disease.