What classification would likely be assigned to a tumor where cells are not expressing cadherin proteins?

The classification of a tumor where cells are not expressing cadherin proteins would most likely be assigned as malignant. Cadherins are a type of cell adhesion molecule crucial for maintaining proper cell-to-cell connections and tissue architecture. In healthy tissues, cadherins facilitate strong adhesion between cells, which helps keep tissues organized and functioning correctly.

When cadherins are not expressed or are dysfunctional, the integrity of cell adhesion is compromised. This lack of adhesion can lead to uncontrolled cell growth, as the cells can lose their anchorage dependence—a hallmark of malignant tumors. Malignant tumors can invade surrounding tissues and have the potential to spread to other parts of the body, which aligns with the loss of cadherins that often correlates with increased proliferative and invasive capabilities.

In contrast, benign tumors are typically well-organized and do not invade neighboring tissues, and they usually maintain normal cell adhesion characteristics. Metastatic tumors refer specifically to cancer cells that have spread from the original (primary) site to distant sites, and pre-cancerous lesions signify changes that may lead to cancer but are not yet classified as malignant. Therefore, the significant loss of cadherin expression strongly points toward a malignant classification due to the association between this loss and aggressive tumor behavior.