Nuclear localization of epidermal growth factor and epidermal growth factor receptors in human thyroid tissues

Epidermal growth factor (EGF) has widespread growth effects, and in some ti ssues proliferation is associated with the nuclear localization of EGF and epidermal growth factor receptor (EGFR). Ln the thyroid, EGF promotes growt h but differs from thyrotropin (TSH) in inhibiting rather than stimulating functional parameters. We have therefore studied the occurrence and cellula r distribution of EGF and EGFR in normal thyroid, in Graves' disease, where growth is mediated through the thyrotropin receptor (TSHR), and in a varie ty of human thyroid tumors. In the normal gland the staining was variable, but largely cytoplasmic, for both EGF and EGFR. In Graves' disease there wa s strong cytoplasmic staining for both EGF and EGFR, with frequent positive nuclei. Nuclear positivity for EGF and particularly for EGFR was also a fe ature of both follicular adenomas and follicular carcinomas. Interestingly nuclear staining was almost absent in papillary carcinomas. These findings document for the first time the presence of nuclear EGF and EGFR in thyroid . Their predominant occurrence in tissues with increased growth (Graves' di sease, follicular adenoma, and carcinoma) may indicate that nuclear EGF and EGFR play a role in growth regulation in these conditions. The absence of nuclear EGF and EGFR in papillary carcinomas would suggest that the role pl ayed by EGF in growth control differs between papillary carcinoma and folli cular adenomas/carcinomas of the thyroid.