Infiltrative

In pathology, infiltrative is a term pathologists use to describe cells, typically cancer cells, that have spread beyond their original location and are now growing into surrounding healthy tissue. When a tumor is described as infiltrative, it means the cancer cells do not have clear borders and instead extend irregularly into nearby tissues, making it challenging to determine precisely where the tumor ends and healthy tissue begins.

The term infiltrative is very similar to the terms invasive or invasion, all of which indicate that cancer cells are spreading into neighboring healthy areas. An infiltrative tumor is usually considered more aggressive because its irregular growth pattern can make treatment more complex.

Does infiltrative mean cancer?

In pathology reports, when describing a tumor, the term infiltrative is almost always associated with malignant (cancerous) tumors. Benign (noncancerous) tumors rarely, if ever, show an infiltrative growth pattern. Benign tumors typically grow slowly and remain well-circumscribed, meaning they are separated from surrounding tissue, unlike infiltrative cancerous tumors.

Pathologists carefully examine the microscopic features of cells and their growth patterns to determine whether a tumor is benign or malignant. Seeing an infiltrative growth pattern strongly suggests the tumor is malignant, meaning it is cancer.

Why is the term infiltrative important?

Identifying a tumor as infiltrative is important because it affects how doctors plan treatment. Infiltrative tumors are usually more aggressive, can be harder to remove surgically, and carry a higher risk of recurrence (the cancer coming back after treatment). Knowing a tumor is infiltrative helps doctors develop the most effective treatment approach and carefully monitor patients over time.

Common cancers described as infiltrative

Several common types of cancers often show an infiltrative growth pattern:

• Invasive ductal carcinoma of the breast: The most common type of breast cancer, characterized by tumor cells spreading into the surrounding breast tissue.

• Glioblastoma: A type of brain cancer that extends irregularly into normal brain tissue, making complete surgical removal challenging.

• Infiltrative type basal cell carcinoma: A type of skin cancer known for spreading unevenly into surrounding healthy skin layers.

How is infiltrative different from well-circumscribed?

An infiltrative tumor lacks distinct borders and blends irregularly with the surrounding healthy tissue. In contrast, a tumor described as well-circumscribed has clear and distinct boundaries, making it easier to separate from normal tissue during surgery. Well-circumscribed tumors are typically benign or less aggressive, while infiltrative tumors are usually malignant (cancerous), more aggressive, and require more intensive treatment.

Understanding whether a tumor is infiltrative helps doctors better predict its behavior and guides decisions about the most appropriate treatment plan.