Overcoming an obstacle in expanding a UMLS semantic type extent

► A problem is shown in a method for finding concepts that are missing a semantic type. ► Concepts assigned the UMLS Semantic Network type ''Classification” form obstacles. ► A method is presented that by passes such obstacles without an explosion in work load. ► This new expansion method found over 500 concepts missing a semantic type. ► The semantic type Experimental Model of Disease was assigned to those 500 concepts.