The results of studying the distribution characteristics of MED12 mutations, X-chromosome inactivation patterns on which the MED12 gene is mapped, as well as chromosome analysis data convincingly prove that LM is a monoclonal disease; however, tumor cell clones in different myomatous nodes may be different, i.e., have different mutations that determine the individual characteristics of molecular pathogenesis. This evidence concerns the gene MED12 and lymphangioma.