Improved detection of clonality in cutaneous T-cell lymphomas using laser capture microdissection.

Abstract

The diagnosis of cutaneous T-cell lymphoma is a challenge for both the pathologist and the clinician. This is particularly true for distinguishing early-stage mycosis fungoides from dermatitis. In this clinical setting, the presence of a clonal T-cell population supports lymphoma. Usually, routinely processed paraffin-embedded material is available for gene rearrangement analysis, and polymerase chain reaction (PCR)-based methods to assess clonality can be performed. One drawback of this approach is that sensitivity is suboptimal in biopsy specimens in which the lymphocytic infiltrate represents only a small percentage of all cells present. Another drawback is that DNA extraction from routinely processed, paraffin-embedded tissue is a time-consuming and labor-intensive procedure which can take up to 5 days in our laboratory. To bypass these problems, we used laser capture microdissection (LCM) to obtain lymphocytic infiltrates from tissue sections of formalin-fixed, paraffin-embedded skin biopsy specimens. This approach allows for more specific PCR assessment of the lymphocytic infiltrate and for rapid DNA extraction and PCR analysis. Using the LCM approach, we could demonstrate clonal T-cell receptor gamma gene rearrangements in biopsy specimens that did not show clonality using DNA extracted by conventional methods from full tissue sections. In addition, DNA extraction and PCR analysis can be performed in 11 h. In conclusion, applying LCM to clonality analysis of cutaneous lymphocytic infiltrates is rapid and more sensitive than conventional methods, and we recommend introducing this approach into the routine diagnostic setting.