Estrogen receptor protein in malignant carcinoid tumor: a report of 2 cases

Two cases of metastatic malignant carcinoid tumor in elderly women contained significant amounts of estrogen receptor (19 and 32 femtomoles/mg protein) as shown by Scatchard-plot analysis of a dextran-coated charcoal assay, inhibition of binding by an estrogen analog (67 and 63%) and high-affinity binding (Kd = 6.8 and 2.6 x 10(-10) M). The demonstration of estrogen receptor in malignant carcinoid tumor expands the spectrum of non-breast or non-gynecologic neoplasms that contain the receptor. The significane of estrogen receptor in such tumors is uncertain; it may represent aberrant derepression of the gene for estrogen receptor protein in a malignant tumor.