Digital pathology is a new branch of medical imaging referring to the aggregation of equipment and software to acquire, store and display microscopic images in a distributed network environment. This article proposes an architecture and describes the implementation of a collaborative pathology web platform. The solution brings the modern collaborative concept, common in social and business networks, into Digital Pathology workflows supported by a customised PACS-DICOM infrastructure. The system assures services like the creation of working sessions, users groups, access control to sessions, synchronisation of operations in a rich web interface, replaying of the actions performed in a session, among others. The solution data management is ensured by a PACS compliant with the DICOM standard, more concretely the recent Whole Slide Imaging format and the DICOM Web communication services.