ABSTRACT
All solid neoplasms have a parenchyma that comprises the neoplastic proliferating cells and a stroma that consists of the supporting connective tissue and blood supply required for growth. Based on the biological behavior of the parenchyma, solid tumors may be classified into three main groups. At one extreme are
benign
tumors that may
arise in any tissue, grow only locally and slowly, and cause damage (which may be significant) by local pressure or obstruction. Patient survival rates are generally high after surgical removal of benign tumors. The second group contains
in-situ
tumors that develop in the epithelium and have the morphological appearance of cancer cells. However, these cells remain in the epithelial layer without invading the basement membrane and supporting mesenchyme. When they acquire the ability to penetrate the basement membrane they become invasive
malignant
tumors that may arise in any tissue
,
grow rapidly, invade, and destroy the underlying local mesenchyme. They often migrate to local lymph nodes and distant organs where they produce secondary tumors.
