GIANT-CELL TUMOR OF TENDON SHEATH IS A POLYCLONAL CELLULAR PROLIFERATION

Giant cell tumor of tendon sheath (GCTTS) is a common soft tissue tumo r. Immunophenotypical evidence suggests it is of synovial cell origin. There is controversy regarding the underlying nature of this lesion, specifically whether it is a neoplastic or nonneoplastic (ie, reactive or hyperplastic) process. Karyotypic abnormalities have been identifi ed in GCTTS and interpreted as evidence of neoplasia, although the fin ding of similar karyotypic abnormalities in unequivocally nonneoplasti c proliferations raises questions about using such finding to define a neoplasm. In an attempt to resolve this uncertainty, a polymerase cha in reaction (PCR)-based assay for methylation of the X-linked human an drogen receptor gene (HUMARA) was used to assess whether GCTTS is a cl onal or polyclonal proliferation. DNA was isolated from formalin-fixed , paraffin-embedded tissue blocks from eight cases of digital GCTTS in female subjects; two cases of hepatocellular carcinoma (HCC) were use d as clonal controls. Seven of eight cases of GCTTS were informative, and each showed a polyclonal proliferation, whereas both cases of HCC were clonal. Our results indicate that GCTTS is a nonneoplastic prolif eration, if one accepts that a population of cells forming a tumorous mass must show clonality to be classified as a neoplasm. Our results e mphasize that simple karyotypic abnormalities do not define a neoplasm . It remains to be determined whether GCTTS is a reactive or hyperplas tic process. HUM PATHOL 28:815-819. Copyright (C) 1997 by W.B. Saunder s Company.