tumorinfiltrate

Tumorinfiltrate, commonly referred to as tumor infiltrate, denotes the invasion of malignant cells into surrounding normal tissue. It reflects the local invasive spread of a tumor beyond its capsule or original mass and is assessed in histopathology to gauge the extent of invasion.

Histologic patterns include cohesive invasion forming strands or nests, or single-cell infiltration; desmoplastic stroma; invasion of fat, muscle, nerves (perineural invasion), or vessels (lymphovascular invasion). Tumor budding is a term for small clusters at the invasive front and is often linked to poor prognosis.

Clinical significance: in surgical pathology, infiltration affects margins and staging (for example, depth of invasion and T stage); the presence of perineural or lymphovascular invasion is associated with a higher risk of recurrence and metastasis. Infiltration patterns can influence treatment decisions, such as the need for wider surgical margins or adjuvant therapy.

Tumor infiltrates include not only malignant cells but also immune cells within the tumor microenvironment, known as tumor-infiltrating lymphocytes (TILs). The composition and density of these infiltrates can influence prognosis and response to therapy in various cancers.

Pathophysiology: invasion is mediated by proteases such as matrix metalloproteinases and by cellular processes like epithelial-mesenchymal transition, which facilitate movement through the extracellular matrix and surrounding tissues. Interactions with the surrounding stroma and vasculature support the invasive process.

See also: tumor microenvironment; tumor-infiltrating lymphocytes; cancer invasion and metastasis.