DSDM (Digital Slide Dynamic Morphometry): targeting tumor budding in colorectal cancer.

Background: In histopathology, quantitative assessment of various morphologic features is based on published methods that were conceived on specific areas observed through the microscope and microscopical objective used. Failure to reproduce the same reference field size if using a different microscope may change the score assessed. When visualizing a digital slide on a computer screen, through a dedicated viewer, it is possible to select the adequate objective-magnification (zoom toolbar). However, the field of view is rectangular, different from the circular field area viewed by optical microscopy. In addition, the evaluation of the size of the selected area of the digital slide is not immediately evident and must be estimated with the draw functions of the viewer or the scale/axes grid. Methods: Using the tools offered by ImageScope, the virtual slide viewer of Aperio Technologies (Vista, USA), a system was conceived to reproduce the various methods published for assessing tumor budding, an important prognostic factor in colorectal cancer. Each method, based on counting tumor budding within a specific area, was reproduced as a colored circle, corresponding to a graphic overlay layer. The various circles were grouped in a target-like shape and then exported and saved as an .xml file. A web page was created giving access to 100 whole-slide digital scans. When each digital slide was opened the file containing the target-like area had to be imported in order to move it onto a tumor budding “hot spot” and to perform the measurements. Eighteen international experts in gastrointestinal pathology were invited to participate. Results: Twelve investigators completed the task, the majority of them performing the multiple assessments of each case in less than 12 minutes. Conclusions: The assessing system proposed appeared to be feasible for pathologists. It allows precise application of methods originally conceived for optical microscopy. The graphical layers that make the tool are freely moved within the digital slide: this system was named DSDM (Digital Slide Dynamic Morphometry). This telepathology extension has various potential applications and might be a useful tool for histopathological assessment of diagnostic parameters that need to be quantified.