EGF and thyroid gland undifferentiated (anaplastic) carcinoma: Notably, the proHB-EGF immunoreactivity in undifferentiated thyroid carcinoma tissues was not always detected, suggesting that less proHB-EGF immunoreactivity in the undifferentiated carcinomas might be due to the active processing of proHB-EGF to sHB-EGF on the cell surface.