1. An interactive coomputerized system for performing a differential dermatopathological diagnosis of a biopsy based on characteristics of said biopsy product, said system comprising an output means for presenting a set of plurality of selected histopathological changes to an operator; an input means for entering operator selected responses; a memory means for storing a hierarchical data base, said data base comprised of a plurality of downwardly linked files, each file comprised of a header record and a plurality of data records, said operator selected response corresponding to one of said data records, said header record comprised of a file identification field and a field for containing the number of the data records located in the file, and each said data record comprised of a linking identifier field and a data field, said data field containing a histopathological change when said identifier field contains an entry of a file identifier that points to a data record located below in the hierarchy and containing a differential diagnosis when said identifier field does not contain said file identifier; and processor means under a programmed control for receiving operator entered responses, for responding to the contents of the identifier field of said operator selected record for retrieving the linked file stored elsewhere in said memory means, and for providing the data stored in said linked file to said output means.