Pathogenic variants in the receptor tyrosine kinase TIE2, encoded by TEK, are known to cause vascular malformations (VMs). In this study, we retrospectively reviewed the deidentified data generated through clinical NGS testing in our laboratory and found 88 VM cases with a total of 107 clinically significant TEK variants. Among those, 23 unique variants at the amino acid level were identified, including five novel (p.Cys1040Arg, p.Arg1099PhefsTer12, p.Glu1109Ter, p.Phe1111LeufsTer7, p.Phe1111ValfsTer7) and 18 previously published variants. Missense variants were identified more often in the tyrosine kinase domain, while all nonsense/frameshift variants were clustered in the C-terminal tail (CTT). In addition, most variants occurred as solitary alterations, whereas certain variants always co-occurred with a second TEK variant. Five patterns of TEK variants (P1-P5) were identified: (P1) Arg849 + another variant
(P2) Tyr897 + another variant
(P3) Leu914 single variants
(P4) Arg915/918 single variants
and (P5) CTT single /co-occurring variants. This study provides the most comprehensive view of pathogenic TEK variants in VMs to date.