MMP1 and cyst: Immunohistochemical staining including factor VIII, podoplanin, endothelial markers (CD31, CD34, ERG avian V‐ets erythroblastosis virus E26 oncogene homolog), FLI1 (“friend leukemia factor”), and matrix metalloproteinase‐1 (MMP-1) can help to identify cAS in the cyst walls [17, 18].