Clonality testing of cutaneous lymphoid infiltrates: practicalities, pitfalls and potential uses

PCR is the method of choice for assessing antigen receptor gene rearrangement in suspect cutaneous infiltrates. It is a powerful and robust technique, but not without certain limitations and pitfalls. Of particular importance in the analysis of lymphoproliferations in the skin are the quality of DNA obtainable, an understanding of how primer choice may influence sensitivity and issues surrounding pseudoclonality. When interpreting results, cognisance must also be taken of the well-documented fact that monoclonal T-cell receptor and immunoglobulin gene rearrangements are not infrequently encountered in benign reactive cutaneous disorders. We discuss these issues in detail herein, and outline the situations in which we believe clonality testing may add value to assessing the biological nature of a cutaneous lymphoid infiltrate. Lastly, we emphasize the importance of interpreting any results derived from PCR assays in the context of the clinical, histological and immunophenotypic findings.