MTSS1 (Metastasis suppressor 1), also known as Missing in metastasis (MIM), is a tissue-specific regulator of plasma membrane dynamics. MTSS1 is well described for its function as a metastasis suppressor gene and is expressed in a variety of tissues. MTSS1 might be involved in shaping neuronal membranes in vivo. MTSS1 deforms phosphoinositide-rich membranes through its I-BAR domain and interacts with actin monomers through its WH2 domain. MTSS1/MIM was first identified as a metastasis suppressor missing in metastatic bladder carcinoma cell lines. MTSS1 is a prognostic indicator of disease-free survival in breast cancer patients and demonstrates the ability to play a role in governing the metastatic nature of breast cancer cells. MTSS1 may serve as a useful biomarker for the prediction of the outcome of gastric cancer. The down-regulation of MTSS1 that may be caused by DNA methylation was also observed in many other types of cancer. Recent work proposed that MIM also potentiates Sonic hedgehog (Shh)-induced gene expression. MTSS1 is a multiple functional molecular and has an important role in development, carcinogenesis, and metastasis.