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Pronunciation: in-va'zhun


  1. The beginning or incursion of a disease.
  2. Local spread of a malignant neoplasm by infiltration or destruction of adjacent tissue; for epithelial neoplasms, invasion signifies infiltration beneath the epithelial basement membrane.
  3. Entrance of foreign cells into a tissue, such as polymorphonuclear leukocytes in inflammation.

[L. invasio, fr. in-vado, pp. -vasus, to go into, attack]

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© Copyright 2018 Wolters Kluwer. All Rights Reserved. Review date: Sep 19, 2016.