NRAS mutation in a central conducting lymphatic anomaly and PPFIBP1::ROS1 fusion in a Gorham-stout disease patient.

Lymphatic malformations (LMs) can lead to severe clinical complications, including disfigurement and even death. While genomic alterations have been identified in LMs, the genomic landscape of complex LMs remains poorly defined due to their rarity. In this study, we report two novel findings: an NRAS p.Q61R mutation in central conducting lymphatic anomaly (CCLA) and a PPFIBP1::ROS1 fusion in Gorham-Stout disease (GSD), both described for the first time in their respective LM subtypes. The discovery of the PPFIBP1::ROS1 fusion provided a unique opportunity to localize the somatic event to a specific cell type. Using serial tissue sections from the same specimen, we observed that the fusion signal was spatially associated with lymphatic endothelial cells, based on serial section analysis with D2-40 staining. Given that both NRAS mutations and PPFIBP1::ROS1 fusions have also been identified in other LM subtypes, our findings support the hypothesis that LMs may share common molecular mechanisms. We propose that phenotypic diversity among LM subtypes may arise from differences in developmental timing, anatomic location, and microenvironmental context at the time the somatic mutation occurs.