Cytoplasmic p21 expression can be significantly correlated with lymph node metastasis, distant metastases, advanced TNM stage (a classification of cancer staging that stands for: tumor size, describing nearby lymph nodes, and distant metastasis), depth of invasion and OS (overall survival rate). A study on immunohistochemical markers in malignant thymic epithelial tumors shows that p21 expression has a negatively influenced survival and significantly correlated with WHO (World Health Organization) type B2/B3. When combined with low p27 and high p53, DFS (Disease-Free Survival) decreases.