MMP9 and neoplasm: Fassina et al. were able to show that tumors of the most-aggressive sarcomatoid subtype showed higher expression of EMT transcriptional regulators (e.g., SNAIL, SLUG, TWIST) and higher expression of mesenchymal markers (such as vimentin and MMP9) compared with tumors of the biphasic and epithelioid subtypes [28], which further confirms the importance of TGF-β in PM tumor growth and invasion.