Estrogen receptor expression in giant cell tumors of the bone

Giant cell tumors (GCTs) of the bone are primary skeletal neoplasms that behave intermediately between a true benign and an overtly malignant neoplasm. For two decades, controversial reports have found estrogen receptor (ER) expression in isolated cells or small numbers of samples from these tumors. In this report, we studied by immunohistochemistry 88 cases of GCTs and found that 51% of the samples expressed ER. Furthermore, we found that a subset of seven samples analyzed for ER expression by western blot was positive. To address whether the ER expressed in these samples could be functional, isolated cells were exposed to beta-estradiol and growth curves were generated. Exposure of cells to beta-estradiol induced a small but significant growth in the cells. These results strongly support that GCTs of the bone express functional ERs.