Abstract
The problem of differential diagnosis in breast histopathology is described and areas in need of decision support identified. It is argued that the conventional role played by decision support systems, i.e. that of the ‘autonomous problem-solver’, is unacceptable in this domain and that support must be given to the actual cognitive functions of potential system users. Decision-making processes of pathologists are examined with particular reference to Rector's category of ‘broad experts’. Pathologists possess a rich set of general diagnostic concepts for their domain, but their knowledge of detailed aspects of differential diagnosis may contain gaps and errors. A cooperative model of decision support, which utilizes the strengths and complements the weaknesses of pathologists' problem-solving skills, is described and the operation of this model within a functioning system illustrated.