The present invention provides impedance data having an improved spatial resolution, both with regard to depth and lateral extension, which enables a detection of diseased skin conditions, such a malignant melanoma, at an early stage. Specifically, the present invention is implemented in a probe, medical devices and medical systems including such a probe, and methods using such a probe for measuring electrical impedance of tissue of a subject. A switching circuit is arranged for selectively activate electrode pairs of the probe in accordance with a predetermined activation scheme, the predetermined activation scheme including to activate adjacent electrodes in a successive manner, to gradually scan tissue of the subject at a first tissue depth so as to obtain a sequence of impedance signals from the tissue depth.