Metastasis
Metastasis (pronounced meh-TAS-ta-sis) meansspreadcancer. Cancer cells can break away fromprimary tumortravel throughbloodstream or lymphatic systemother parts ofbody. The pluralmetastases (pronounced meh-TAS-ta-seez).
Cancerscapablespreading throughbody by two mechanisms: invasionmetastasis. Invasion isdirect migrationpenetration by cancer cells into neighboring tissues. Metastasis isabilitycancer cellspenetrate into lymphaticblood vessels, circulate throughbloodstream,then grow innew focus (metastasize)normal tissues elsewhere inbody.
Tumorsclassified as being either benign or malignant depending on whether or notcan spread by local invasion and/or metastasis. Benign tumorstumors that cannot spread by invasion or metastasis; henceonly grow locally. Malignant tumorstumors thatcapablespreading by invasionmetastasis. By definition,term "cancer" applies onlymalignant tumors.
When patientsdiagnosedcancer,wantknow whether their diseaselocal or has spreadother locations.
Itits abilityspreadother tissuesorgans that makes cancerpotentially life-threatening disease, so theregreat interestunderstanding what makes metastasis possible forcancerous tumor.
Cancer cells may spreadlymph nodes nearprimary tumor (regional lymph nodes). Thiscalled nodal involvement, positive nodes, or regional disease. Cancer cells can also spreadother parts ofbody, distant fromprimary tumor. Doctors useterm metastatic disease or distant diseasedescribe cancer that spreadsother organs orlymph nodes other than those nearprimary tumor.
When cancer cells spreadformnew tumor,new tumorcalledsecondary, or metastatic, tumor. The cancer cells that formsecondary tumorlike those inoriginal tumor. That means,example, that if breast cancer spreads (metastasizes) tolung,secondary tumormade upabnormal breast cells (not abnormal lung cells). The disease inlungmetastatic breast cancer (not lung cancer).
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2 Metastasisprimary cancer 3 Diagnosisprimarysecondary tumors 4 Treatmentsmetastatic cancer |
Factors involvedmetastasis
Metastasis iscomplex seriesstepswhich cancer cells leaveoriginal tumor sitemigrateother parts ofbody viabloodstream or lymph system. To do so, malignant cells break away fromprimary tumorattachand degrade proteins that make upsurrounding extracellular matrix (ECM), which separatestumor from adjoining tissue. By degrading these proteins, cancer cellsablebreachECMescape. When oral cancers metastasize,commonly travel throughlymph system tolymph nodes inneck.
Cancer researchers studyingconditions necessarycancer metastasis have discovered that one ofcritical events required isgrowth ofnew networkblood vessels. This processforming new blood vesselscalled angiogenesis.
Tumor angiogenesis isproliferation ofnetworkblood vessels that penetrates into cancerous growths, supplying nutrientsoxygenremoving waste products. Tumor angiogenesis actually startscancerous tumor cells releasing molecules that send signalssurrounding normal host tissue. This signaling activates certain genes inhost tissue that,turn, make proteinsencourage growthnew blood vessels.
Metastasisprimary cancer
Metastatis theoretically always coincides withprimary cancer. It istumor that started fromcancer cell or cellsanother part ofbody. However, over 10%patients presentingoncology units will have metastases withoutprimary tumour found. Studies have shown that if simple questioning does not revealcancer's source (coughing up blood -\'probably lung', urinating blood - 'probably bladder'), complex imaging will not either. In somethese casesprimary will appear later.
The useimmunohistochemistry has permitted pathologistsgive an identitymanythese metastases. Imaging ofindicated area only occasionally revealsprimary however.
Diagnosisprimarysecondary tumors
The cells inmetastatic tumor resemble those inprimary tumor. Oncecancerous tissueexamined undermicroscopedeterminecell type,doctor can usually tell whether that typecellnormally found inpart ofbody from whichtissue sample was taken.
For instance, breast cancer cells looksame whether theyfound inbreast or have spreadanother part ofbody. So, iftissue sample taken fromtumor inlung contains cells that look like breast cells,doctor determines thatlung tumor issecondary tumor.
Metastatic cancers may be found atsame time asprimary tumor, or months or years later. Whensecond tumorfound inpatient who has been treatedcancer inpast, itmore oftenmetastasis than another primary tumor.
In about 10%cancer patients,secondary tumordiagnosed, but no primary cancer can be found,spiteextensive tests. Doctors refer toprimary tumor as unknown or occult, andpatientsaidhave cancerunknown primary origin (CUP). In rare cases (e.g.melanoma) no primary tumorfound even on autopsy. Ittherefore thought that some primary tumors can regress completely, but leave their metastases behind.
Treatmentsmetastatic cancer
When cancer has metastasized,may be treatedchemotherapy, radiation therapy, biological therapy, hormone therapy, surgery, orcombinationthese. The choicetreatment generally depends ontypeprimary cancer,sizelocation ofmetastasis,patient's agegeneral health, andtypestreatments used previously. In patients diagnosedCUP, itstill possibletreatdisease even whenprimary tumor cannot be located.
