The design and implementation of a web-based diagnostic support tool for melanoma dermatological images and related diagnostic data is presented. The proposed system is semantic web-based and is driven by exploiting the combination of AJAX framework and topic map technology. A novel client/server architecture was developed that enables several clients to interact online with the topic map-based system. Users have the ability to access the system anywhere and anytime via a simple Internet browser. Additionally, an ABCD application has been developed for automated calculation of ABCD parameters and consequently embedded in the proposed TM-based system.