Background: The cBioPortal is a prevalent open-source translational research platform, allowing private instances and extensions.

Objective: Our aim was to build up an own instance of cBioPortal, identify missing functionality by interviewing researchers, and implementing these extensions.

Methods: We examined the code base of the cBioPortal and conducted a requirements analysis with researchers. Then an own extension was implemented and a usability evaluation was performed.

Results: We developed a new tab in the results view of cBioPortal adding the option to analyze the correlation of gene expression and mutation patterns.

Conclusion: While extending the cBioPortal is possible, there are still some challenges to overcome. A plug-in concept and a more detailed documentation would greatly facilitate the development of own extensions.