A mains electricity (AC-powered) instrument intended to measure/map the differences in capacitance and resistance between neoplastic and surrounding normal tissue, using electrical impedance spectroscopy (EIS). It is designed to provide real-time, noninvasive, radiation-free, multi-frequency measurement and/or imaging of local distributions of tissue electrical impedance by applying and detecting a low-voltage electrical signal through the skin, via an electrode, and displaying the results on a monitor. It is intended to indicate cytological and histological tissue changes typically in combination with other methodologies (e.g., mammography, visual examination).