**Core Concept**
E-Cadherin is a transmembrane glycoprotein involved in cell-cell adhesion, playing a crucial role in maintaining tissue architecture and preventing tumor cell invasion and metastasis. Loss or downregulation of E-Cadherin expression is associated with increased tumor aggressiveness and poor prognosis in various cancers.

**Why the Correct Answer is Right**
E-Cadherin's role in tumor metastasis lies in its ability to mediate cell-cell adhesion, which is essential for maintaining tissue integrity. When E-Cadherin expression is reduced or lost, cancer cells can detach from the primary tumor site, invade surrounding tissues, and migrate to distant organs, leading to metastasis. This process is often accompanied by epithelial-to-mesenchymal transition (EMT), a key event in tumor progression.

**Why Each Wrong Option is Incorrect**
**Option A:** Fibronectin is a glycoprotein involved in cell adhesion, migration, and wound healing, but it is not directly involved in the tumor metastasis cascade.
**Option C:** Type IV collagenase, also known as matrix metalloproteinase-9 (MMP-9), is an enzyme involved in the degradation of the extracellular matrix and basement membrane, facilitating cancer cell invasion and metastasis. However, it is not the primary protein involved in cell-cell adhesion and tumor metastasis.
**Option D:** Tyrosine kinase is a family of enzymes involved in signal transduction and cell proliferation, but it is not directly involved in the tumor metastasis cascade.

**Clinical Pearl / High-Yield Fact**
Loss of E-Cadherin expression is a common feature in various cancers, including breast, lung, and colorectal cancer, and is often associated with poor prognosis and reduced overall survival. Therefore, E-Cadherin is a valuable prognostic marker and potential therapeutic target in cancer treatment.

✓ Correct Answer: B. E-Cadherin