Percentage of {gamma}{delta} T cells in panniculitis by paraffin immunohistochemical analysis.

Cutaneous T-cell lymphomas with panniculitis-like histologic features have different clinical courses depending on whether they are composed of alphabeta T cells or gammadelta T cells, necessitating their distinction for proper prognostication. However, unlike alphabeta T cells, gammadelta T cells cannot be reliably detected in formalin-fixed, paraffin-embedded sections. We demonstrated that a commercially available antibody can detect gammadelta T cells and examined 2 cases of flow cytometry-proven gammadelta T-cell lymphomas and 15 control cases of nonneoplastic panniculitis. In both lymphomas, the atypical lymphocytes were gammadelta T cells, whereas the reactive lymphocytes were alphabeta T cells. In contrast, nonneoplastic panniculitis had predominantly alphabeta T cells with many fewer and individually scattered gammadelta T cells. The detection of gammadelta T cells in paraffin sections provides a powerful new tool to characterize T cells in lymphomas and inflammation.