Integrating Patient-Reported Outcome Measures (PROMs) into Molecular Tumor Boards (MTBs) remains challenging due to the complexity of data visualization and integration into clinical workflows. This work, as part of the German PM4Onco project, aims to identify visualization requirements for PROMs and develop a prototype for PROMs integration in cBioPortal, facilitating broader application within oncology care. We employed a qualitative research approach, including developing personas for MTB stakeholders, conducting a literature-based requirements analysis, organizing a co-design workshop to create low-fidelity prototypes, and evaluating the highest-rated prototype variant through an online survey distributed to MTB physicians across Germany. Seven specialist groups were identified, with key needs including intuitive visualization, clear axis labeling, and longitudinal symptom tracking. The resulting mid-fidelity mockup incorporated PROMs data within cBioPortal's timeline view and a detailed PROMs tab, featuring trend indicators, line graphs, and customizable health displays. Usability evaluation by MTB members yielded a SUS score of 67, indicating an initial indicator of acceptable usability, with suggestions for improvements like threshold scores and deeper clinical data integration. While PROMs offer critical patient insights, they remain underused in MTBs. Our early-stage prototype demonstrates potential for addressing this gap, with future work focusing on implementation, broader testing, and international validation.