Citations

Klippel-Trénaunay syndrome (KTS) is a rare congenital vascular-overgrowth disorder within the broader spectrum of PIK3CA -related overgrowth syndromes. Although clinical, radiologic, and orthopedic manifestations are well described, the histologic spectrum of KTS-associated pathology remains under-characterized. Clinicopathologic findings from 21 patients with clinically established KTS were reviewed, including 18 with longitudinal clinical follow-up and 3 consultation cases of rare malignant mesenchymal neoplasms. Cases were identified from institutional pathology and clinical databases, and available hematoxylin and eosin-stained sections and ancillary studies were reviewed. The cohort included 11 males and 10 females. Among the 18 clinically followed patients, 12 had limb length discrepancy or asymmetric limb overgrowth, 9 had documented deep vascular malformations, 4 had intra-articular/synovial malformations, and 10 underwent initial orthopedic evaluation or intervention before age 18. Orthopedic morbidity clustered into mechanical overgrowth-related, vascular malformation-related, and soft tissue/wound-related complications. Histologic findings included superficial and/or deep slow-flow vascular malformations, ulceration and granulation tissue, hemosiderin-laden reactive synovium, and destructive hemorrhagic arthropathy. Intra-articular disease recapitulated a hemophilic arthropathy-like pattern, with hemosiderotic synovitis, papillary synovial hyperplasia, and progressive joint destruction with loss of articular cartilage, exposed subchondral bone destruction and remodeling, all attributable to long-standing intra-articular hemorrhage. Three consultation cases showed malignant mesenchymal neoplasia, including 2 angiosarcomas. Recognition of these patterns is important for pathologists evaluating specimens from patients with known or suspected KTS, particularly when findings mimic hemophilic arthropathy, diffuse-type tenosynovial giant cell tumor, nonsyndromic vascular malformation, and/or end-stage destructive arthropathy.

Abstract Oncogenic translocations involving the MET gene have been reported in several cancer types, but detailed clinicogenomic characterization of these cancers is not well defined. In addition, prospective clinical trials evaluating the antitumor activity of MET inhibitors in MET rearrangement–positive cancers are limited. In this study, in a pan-cancer analysis of >46,000 solid tumors with comprehensive genomic profiling, we identified oncogenic MET rearrangements in ∼0.04% of cancers. Preliminary analysis from a phase II clinical trial of the type I MET tyrosine kinase inhibitor (TKI) vebreltinib in MET fusion–positive solid tumors demonstrated an objective response rate of 50% and disease control rate of 79%, with antitumor activity seen in diverse cancer types, including lung adenocarcinoma and intrahepatic cholangiocarcinoma, among others. Similar to MET exon 14–altered lung cancer, secondary mutations in the kinase domain can confer resistance to MET TKIs in MET fusion–positive cancers. Overall, these data categorize MET rearrangements as actionable targets in solid tumors. Significance: MET rearrangement–positive cancers are not well-characterized, and optimal treatment strategies are yet to be defined. Through comprehensive genomic analysis, preclinical modeling, and preliminary results of a phase II clinical trial, we demonstrate that MET fusions are a unique molecular subtype of cancers targetable with vebreltinib, a TKI in development.