Invasive cancer
Invasive cancer refers to the process by which cancer cells spread and invade surrounding normal tissues and cells. This stage typically follows the development of cancer in situ (CIS), where abnormal cells are present but have not yet penetrated surrounding tissues. Factors that increase the risk of developing invasive cancer include increased tumor vascularity, loss of cell adhesion, and production of specific enzymes that facilitate tissue breakdown. The transition from CIS to invasive cancer involves significant changes, including alterations in adhesion proteins and the secretion of enzymes that aid in the invasion of nearby tissues, organs, and vessels.
Symptoms of invasive cancer can be nonspecific, often depending on the location and extent of tissue infiltration. The diagnosis of invasiveness is usually confirmed through surgical evaluation and laboratory analysis. Treatment options aim to inhibit tumor invasiveness and may involve biologic therapies, chemotherapy, or radiation. Early detection and removal of cancerous lesions in situ are crucial for prevention, as the presence of invasive cancer complicates treatment and negatively affects prognosis. Understanding the nuances of invasive cancer is essential for effective management and improving patient outcomes.
Subject Terms
Invasive cancer
RELATED CONDITIONS: Cancer in situ, metastatic cancer
DEFINITION: Invasive cancer describes the dispersion and invasion of cancer cells into surrounding normal cells and tissues. It is preceded by cancer in situ (CIS) and precedes metastasis.
Risk factors: Once cancer in situ has developed, the risk of invasive cancer increases with increasing tumor vascularity, loss of cell adhesion molecules, and expression of proteolytic enzymes.
Etiology and the disease process: Invasiveness is a stage of cancer development that is preceded by dysplasia and then by cancer in situ (CIS). Several related changes occur in the transition from CIS to invasive cancer. Normal cell adhesion molecules must be disrupted, and invasive tumor cells show alterations in the integrin and cell adhesion families of proteins. In addition, invasive tumor cells secrete proteolytic enzymes that digest the surrounding extracellular matrix. Invasive tumor cells also secrete motility factors that prompt migration into adjacent tissues. Invasion can be into adjacent organs, blood vessels, or lymphatic vessels. Even though the efficiency with which invasive cancer cells establish metastatic lesions is low, about 60 percent of patients with invasive cancer have overt or occult metastases at diagnosis.
Incidence: At diagnosis, the ratio of localized (preinvasive) cancer to invasive cancer varies from organ to organ. In prostate cancer, for example, between 70 and 90 percent of new cases are confined to the prostate, but only around 13 percent of pancreatic cancers are localized at diagnosis.
Symptoms: Symptoms of invasive cancer are usually nonspecific and related to infiltration of adjacent structures. They depend highly on the identity, vascularization, and innervation of the invaded structures.
Screening and staging: Determination of a tumor’s invasiveness is done in the operating room and the laboratory. At surgery, invasiveness may be present as grossly apparent tumor growth into and around surrounding structures. Microscopic invasiveness is less apparent but contributes to the adherence of tumor cells to surrounding tissue. Diagnosis of invasiveness can also be made by screening blood for the presence of circulating tumor cells.
Treatment and therapy: Therapeutic options directed at inhibiting tumor invasiveness include biologic agents that block growth factor receptors and antibodies that target the integrin family of extracellular adhesion molecules. For example, a blockade of the vitronectin receptor (an integrin) reduces the vascularization of tumor masses and may improve patient outcomes. Radiation may also be employed. Adjuvant therapies may also be beneficial. In stopping cancer spread before metastasis, chemotherapy, immunotherapy, hormone therapies, and targeted therapies are useful as well.
Prognosis, prevention, and outcomes: Tumor invasion complicates complete surgical removal of a tumor and is a precondition for metastases, significantly worsening prognosis. Prevention of invasive cancer requires early detection and removal of cancerous in situ lesions.
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