Cathepsin K expression in a wide spectrum of perivascular epithelioid cell neoplasms ( PEComas): a clinicopathological study emphasizing extrarenal PEComas.

Aims Recent studies have demonstrated that cathepsin K seems to be a powerful marker in identifying renal perivascular epithelioid cell neoplasms ( PEComas). However, the expression in extrarenal PEComas has not been well characterized due to their rare incidence. Our aim was to investigate the expression of cathepsin K in a wide spectrum of extrar-enal PEComas and evaluate its potential diagnostic usefulness in comparison with other commonly used markers. Methods and results Twenty-three cases of PEComa (liver, n = 9; lung, n = 1; broad ligament of uterus, n = 1; vertex subcutaneous soft tissue, n = 1; abdominal wall, n = 1; and kidney, n = 10) were selected for study. All displayed a high percentage of cells with moderately to strongly positive reactions for cathepsin K (mean 91%; range 80-100%). HMB45, Melan-A and smooth muscle actin ( SMA) were expressed in 78, 87 and 87% of cases, respectively, with various percentages of positive cells (mean, 34, 40 and 38%; range 0-80, 0-90 and 0-90%). Transcription factor E3 ( TFE3) was expressed strongly in only three cases; none exhibited evidence of TFE3 gene fusion or amplification. Conclusions Cathepsin K appears to be more powerful than other commonly used markers in diagnosing a wide spectrum of PEComas and distinguishing them from the majority of human cancers. [ABSTRACT FROM AUTHOR]