For the musical composition, see Metastaseis (Xenakis). For the 2009 film, see Metastases (film).
| Metastasis |
| Classification and external resources |
Cut surface of a liver showing multiple metastatic nodules originating from pancreatic cancer |
| DiseasesDB |
28954 |
| MedlinePlus |
002260 |
Metastasis, or metastatic disease (sometimes abbreviated mets), is the spread of a disease from one organ or part to another non-adjacent organ or part.[1][2] It was previously thought that only malignant tumor cells and infections have the capacity to metastasize; however, this is being reconsidered due to new research.[3] In origin metastasis is a Greek word meaning "displacement", from μετά, meta, "next", and στάσις, stasis, "placement". The plural is metastases.
Cancer occurs after a single cell in a tissue is progressively genetically damaged to produce a cancer stem cell possessing a malignant phenotype. These cancer stem cells are able to undergo uncontrolled abnormal mitosis, which serves to increase the total number of cancer cells at that location. When the area of cancer cells at the originating site becomes clinically detectable, it is called a primary tumor. Some cancer cells also acquire the ability to penetrate and infiltrate surrounding normal tissues in the local area, forming a new tumor. The newly formed "daughter" tumor in the adjacent site within the tissue is called a local metastasis.
Some cancer cells acquire the ability to penetrate the walls of lymphatic and/or blood vessels, after which they are able to circulate through the bloodstream (circulating tumor cells) to other sites and tissues in the body. This process is known (respectively) as lymphatic or hematogeneous spread.
After the tumor cells come to rest at another site, they re-penetrate the vessel or walls and continue to multiply, eventually forming another clinically detectable tumor. This new tumor is known as a metastatic (or secondary) tumor. Metastasis is one of three hallmarks of malignancy (contrast benign tumors).[4] Most tumors and other neoplasms can metastasize, although in varying degrees (e.g., basal cell carcinoma rarely metastasize).[4]
When tumor cells metastasize, the new tumor is called a secondary or metastatic tumor, and its cells are similar to those in the original tumor. This means, for example, that, if breast cancer metastasizes to the lungs, the secondary tumor is made up of abnormal breast cells, not of abnormal lung cells. The tumor in the lung is then called metastatic breast cancer, not lung cancer.
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Contents
- 1 Signs and symptoms
- 2 Pathophysiology
- 2.1 Factors involved
- 2.2 Routes of metastasis
- 2.2.1 1. Transcoelomic
- 2.2.2 2. Lymphatic spread
- 2.2.3 3. Haematogenous spread
- 2.2.4 4. Transplantation or implantation
- 2.3 Organ-specific targets
- 2.4 Metastasis and primary cancer
- 2.5 Common sites of origin
- 3 Diagnosis
- 4 Management
- 5 See also
- 6 References
- 7 External links
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Signs and symptoms
Symptoms of cancer metastasis depend location of the tumor.
The symptoms of metastasis varies with location of the tumors.
Initially, nearby lymph nodes are struck early.[5] The lungs, liver, brain, and bones are the most common metastasis locations from solid tumors.[5]
- In lymph nodes, a common symptom is lymphadenopathy
- Lungs: cough, hemoptysis and dyspnea[5] (shortness of breath)
- Liver: hepatomegaly (enlarged liver), nausea[5] and jaundice[5]
- Bones: bone pain,[5] fracture of affected bones[5]
- Brain: neurological symptoms such as headaches,[5] seizures,[5] and vertigo.[5]
Although advanced cancer may cause pain, it is often not the first symptom.
Some patients, however, don't show any symptoms.[5]
Pathophysiology
Metastatic tumors are very common in the late stages of cancer. The spread of metastases may occur via the blood or the lymphatics or through both routes. The most common places for the metastases to occur are the lungs, liver, brain, and the bones.[6]
Factors involved
Metastasis is a complex series of steps in which cancer cells leave the original tumor site and migrate to other parts of the body via the bloodstream, the lymphatic system, or by direct extension. To do so, malignant cells break away from the primary tumor and attach to and degrade proteins that make up the surrounding extracellular matrix (ECM), which separates the tumor from adjoining tissues. By degrading these proteins, cancer cells are able to breach the ECM and escape. The location of the metastases isn't always random, with different types of cancer tending to spread to particular organs and tissues at a rate that is higher than expected by statistical chance alone.[7]. Breast cancer, for example, tends to metastasize to the bones and lungs. This specificity seems to be mediated by soluble signal molecules such as chemokines[8] and transforming growth factor beta[9]. The body resists metastasis by a variety of mechanisms through the actions of a class of proteins known as metastasis suppressors, of which about a dozen are known.[10]
Cancer researchers studying the conditions necessary for cancer metastasis have discovered that one of the critical events required is the growth of a new network of blood vessels, called tumor angiogenesis.[11] It has been found that angiogenesis inhibitors would therefore prevent the growth of metastases.[4]
There are several different cell types critical to tumor growth. In particular endothelial progenitor cells are a very important cell population in tumor blood vessel growth. This finding was published in the journals Science (2008) and Genes and Development (2007) together with the fact that endothelial progenitor cells are critical for metastasis and angiogenesis.[12][13] The importance of endothelial progenitor cells in tumor growth, angiogenesis and metastasis has been confirmed by a recent publication in Cancer Research (August 2010). This seminal paper has demonstrated that endothelial progenitor cells can be marked using the Inhibitor of DNA Binding 1 (ID1). This novel finding meant that investigators were able to track endothelial progenitor cells from the bone marrow to the blood to the tumor-stroma and even incorporated in tumor vasculature. This finding of endothelial progenitor cells incorporated in tumor vasculature proves the importance of this cell type in blood vessel development in a tumor setting and metastasis. Furthermore, ablation of the endothelial progenitor cells in the bone marrow lead to a significant decrease in tumor growth and vasculature development. Therefore endothelial progenitor cells are very important in tumor biology and present novel therapeutic targets.[14]
Routes of metastasis
Main sites of metastases for some common cancer types. Primary cancers are denoted by "
...cancer" and their main metastasis sites are denoted by "
...metastases".
[15]
Metastasis occurs by following four routes:
1. Transcoelomic
The spread of a malignancy into body cavities can occur via seeding the surface of the peritoneal, pleural, pericardial, or subarachnoid spaces. For example, ovarian tumors can spread transperitoneally to the surface of the liver. Mesothelioma and primary lung cancers can spread through the pleural cavity, often causing malignant pleural effusion.[16]
2. Lymphatic spread
Invasion into the lymphatic system allows the transport of tumor cells to regional and distant lymph nodes and, ultimately, to other parts of the body. This is the most common route of metastasis for carcinomas. In contrast, it is uncommon for a sarcoma to metastasize via this route.
Lymph node with almost complete replacement by metastatic melanoma. The brown pigment is focal deposition of melanin
3. Haematogenous spread
This is typical route of metastasis for sarcomas, but it is also the favored route for certain types of carcinoma, such as those originating in the kidney (renal cell carcinoma). Because of their thinner walls, veins are more frequently invaded than are arteries, and metastasis tends to follow the pattern of venous flow.
4. Transplantation or implantation
Mechanical carriage of fragments of tumor cells by surgical instruments during operation or the use of needles during diagnostic procedures.
Cancer cells may spread to lymph nodes (regional lymph nodes) near the primary tumor. This is called nodal involvement, positive nodes, or regional disease. ("Positive nodes" is a term that would be used by medical specialists to describe a patient's condition, meaning that the patient's lymph nodes near the primary tumor tested positive for malignancy. It is common medical practice to test by biopsy at least two lymph nodes near a tumor site when doing surgery to examine or remove a tumor.) Localized spread to regional lymph nodes near the primary tumor is not normally counted as metastasis, although this is a sign of worse prognosis. Transport through lymphatics is the most common pathway for the initial dissemination of carcinomas.[4]
Organ-specific targets
There is a propensity for certain tumors to seed in particular organs. This was first discussed as the "seed and soil" theory by Stephen Paget over a century ago in 1889. For example, prostate cancer usually metastasizes to the bones. In a similar manner, colon cancer has a tendency to metastasize to the liver. Stomach cancer often metastasises to the ovary in women, then it is called a Krukenberg tumor.
According to the "seed and soil" theory, it is difficult for cancer cells to survive outside their region of origin, so in order to metastasize they must find a location with similar characteristics.[17] For example, breast tumor cells, which gather calcium ions from breast milk, metastasize to bone tissue, where they can gather calcium ions from bone. Malignant melanoma spreads to the brain, presumably because neural tissue and melanocytes arise from the same cell line in the embryo.[18]
In 1928 James Ewing challenged the "seed and soil" theory and proposed that metastasis occurs purely by anatomic and mechanical routes.
Metastasis and primary cancer
It is theorized that metastasis always coincides with a primary cancer, and, as such, is a tumor that started from a cancer cell or cells in another part of the body. However, over 10% of patients presenting to oncology units will have metastases without a primary tumor found. In these cases, doctors refer to the primary tumor as "unknown" or "occult," and the patient is said to have cancer of unknown primary origin (CUP) or unknown primary tumors (UPT). It is estimated that 3% of all cancers are of unknown primary origin.[19] Studies have shown that, if simple questioning does not reveal the cancer's source (coughing up blood—"probably lung", urinating blood—"probably bladder"), complex imaging will not either.[19] In some of these cases a primary tumor may appear later.
The use of immunohistochemistry has permitted pathologists to give an identity to many of these metastases. However, imaging of the indicated area only occasionally reveals a primary. In rare cases (e.g., of melanoma), no primary tumor is found, even on autopsy. It is therefore thought that some primary tumors can regress completely, but leave their metastases behind.
Common sites of origin
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This section does not cite any references or sources. (September 2007) |
- Lung
- Breast
- Skin: melanoma (other skin tumors rarely metastasize)
- Colon
- Kidney
- Prostate
- Pancreas
- Cervix
Diagnosis
The cells in a metastatic tumor resemble those in the primary tumor. Once the cancerous tissue is examined under a microscope to determine the cell type, a doctor can usually tell whether that type of cell is normally found in the part of the body from which the tissue sample was taken.
For instance, breast cancer cells look the same whether they are found in the breast or have spread to another part of the body. So, if a tissue sample taken from a tumor in the lung contains cells that look like breast cells, the doctor determines that the lung tumor is a secondary tumor. Still, the determination of the primary tumor can often be very difficult, and the pathologist may have to use several adjuvant techniques, such as immunohistochemistry, FISH (fluorescent in situ hybridization), and others. Despite the use of techniques, in some cases the primary tumor remains unidentified.
Metastatic cancers may be found at the same time as the primary tumor, or months or years later. When a second tumor is found in a patient that has been treated for cancer in the past, it is more often a metastasis than another primary tumor.
It was previously thought that most cancer cells have a low metastatic potential and that there are rare cells that develop the ability to metastasize through the development of somatic mutations.[20] According to this theory, diagnosis of metastatic cancers is only possible after the event of metastasis. Traditional means of diagnosing cancer (e.g. a biopsy) would only investigate a subpopulation of the cancer cells and would very likely not sample from the subpopulation with metastatic potential.[21]
The somatic mutation theory of metastasis development has not been substantiated in human cancers. Rather, it seems that the genetic state of the primary tumor reflects the ability of that cancer to metastasize.[21] Research comparing gene expression between primary and metastatic adenocarcinomas identified a subset of genes whose expression could distinguish primary tumors from metastatic tumors, dubbed a "metastatic signature."[21] Up-regulated genes in the signature include: SNRPF, HNRPAB, DHPS and securin. Actin, myosin and MHC class II down-regulation was also associated with the signature. Additionally, the metastatic-associated expression of these genes was also observed in some primary tumors, indicating that cells with the potential to metastasize could be identified concurrently with diagnosis of the primary tumor.[22]
Expression of this metastatic signature has been correlated with a poor prognosis and has been shown to be consistent in several types of cancer. Prognosis was shown to be worse for individuals whose primary tumors expressed the metastatic signature.[21] Additionally, the expression of these metastatic-associated genes was shown to apply to other cancer types in addition to adenocarcinoma. Metastases of breast cancer, medulloblastoma and prostate cancer all had similar expression patterns of these metastasis-associated genes.[21]
The identification of this metastasis-associated signature provides promise for identifying cells with metastatic potential within the primary tumor and hope for improving the prognosis of these metastatic-associated cancers. Additionally, by identifying the genes whose expression is changed in metastasis offers potential targets to inhibit metastasis.[21]
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Cut surface of a humerus sawn lengthwise, showing a large cancerous metastasis (the whitish tumor between the head and the shaft of the bone)
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Micrograph of thyroid cancer (papillary thyroid carcinoma) in a lymph node of the neck. H&E stain
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CT image of multiple liver metastases
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CT image of a lung metastasis
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Metastasis proven by liver biopsy (tumor (adenocarcinoma) - lower two-thirds of image). H&E stain.
Management
Treatment and survival is determined, to a great extent, by whether or not a cancer remains localized or spreads to other locations in the body. If the cancer metastasizes to other tissues or organs, it usually dramatically decreases a patient's likelihood of survival (i.e. the "prognosis"). However, there are some cancers - such as some forms of leukemia, a cancer of the blood, or malignancies in the brain - that can kill without spreading at all.
Once a cancer has metastasized, it may still be treated with radiosurgery, chemotherapy, radiation therapy, biological therapy, hormone therapy, surgery, or a combination of these interventions ("multimodal therapy"). The choice of treatment depends on a large number of factors, including the type of primary cancer, the size and location of the metastases, the patient's age and general health, and the types of treatments used previously, among others. In patients diagnosed with CUP, it is often still possible to treat the disease even when the primary tumor cannot be located.
The treatment options currently available are rarely able to cure metastatic cancer, though some tumors, such as testicular cancer and thyroid cancer, are usually still curable.
See also
- Disseminated disease
- Brown-Sequard Syndrome (Sections on Cavernous malformation, Germinoma, Renal cell carcinoma and Lung Cancer)
- Brain metastasis
References
- ^ Klein CA (September 2008). "Cancer. The metastasis cascade". Science 321 (5897): 1785–7. doi:10.1126/science.1164853. PMID 18818347.
- ^ Chiang AC, Massagué J (December 2008). "Molecular basis of metastasis". The New England Journal of Medicine 359 (26): 2814–23. doi:10.1056/NEJMra0805239. PMID 19109576.
- ^ Podsypanina K, Du YC, Jechlinger M, Beverly LJ, Hambardzumyan D, Varmus H (September 2008). "Seeding and Propagation of Untransformed Mouse Mammary Cells in the Lung". Science 321 (5897): 1841–4. doi:10.1126/science.1161621. PMC 2694414. PMID 18755941. //www.ncbi.nlm.nih.gov/pmc/articles/PMC2694414/.
- ^ a b c d Kumar, Vinay; Abbas, Abul K; Fausto, Nelson; Robbins, Stanley L; Cotran, Ramzi S (2005). Robbins and Cotran pathologic basis of disease (7th ed.). Philadelphia: Elsevier Saunders. ISBN 978-0-7216-0187-8.
- ^ a b c d e f g h i j k National Cancer Institute: Metastatic Cancer: Questions and Answers. Retrieved on 2008-11-01
- ^ "Metastatic Cancer: Questions and Answers". National Cancer Institute. http://www.cancer.gov/cancertopics/factsheet/Sites-Types/metastatic. Retrieved 2008-08-28.
- ^ Don X. Nguyen and Joan Massagué, Genetic determinants of cancer metastasis, Nature, 2007. http://www.nature.com/nrg/journal/v8/n5/pdf/nrg2101.pdf
- ^ Zlotnik A., Burkhardt A. M., Homey B., Homeostatic chemokine receptors and organ-specific metastasis, Nature reviews, 2007
- ^ Yvette Drabsch, Peter ten Dijke, TGF-β Signaling in Breast Cancer Cell Invasion and Bone Metastasis, J Mammary Gland Biol Neoplasia (2011) 16:97–108
- ^ Yoshida BA, Sokoloff MM, Welch DR, Rinker-Schaeffer CW (Nov 2000). "Metastasis-suppressor genes: a review and perspective on an emerging field". J Natl Cancer Inst. 92 (21): 1717–30. doi:10.1093/jnci/92.21.1717. PMID 11058615. http://jnci.oxfordjournals.org/cgi/content/full/92/21/1717.
- ^ Weidner N, Semple JP, Welch WR, Folkman J (Jan 1991). "Tumor angiogenesis and metastasis—correlation in invasive breast carcinoma". N Engl J Med. 324 (1): 1–8. doi:10.1056/NEJM199101033240101. PMID 1701519. http://content.nejm.org/cgi/content/abstract/324/1/1.
- ^ Gao D et al. (2008). "Endothelial Progenitor Cells Control the Angiogenic Switch in Mouse Lung Metastasis". Science 319 (5860): 195–198. doi:10.1126/science.1150224. PMID 18187653.
- ^ Nolan DJ et al. (2007). "Bone marrow-derived endothelial progenitor cells are a major determinant of nascent tumor neovascularization". Genes & Development 21 (12): 1546–1558. doi:10.1101/gad.436307. PMC 1891431. PMID 17575055. //www.ncbi.nlm.nih.gov/pmc/articles/PMC1891431/.
- ^ Mellick As, Plummer PN et al. (2010). "Using the Transcription Factor Inhibitor of DNA Binding 1 to Selectively Target Endothelial Progenitor Cells Offers Novel Strategies to Inhibit Tumor Angiogenesis and Growth". Cancer Research 70 (18): 7273–7282. doi:10.1158/0008-5472.CAN-10-1142. PMC 3058751. PMID 20807818. //www.ncbi.nlm.nih.gov/pmc/articles/PMC3058751/.
- ^ List of included entries and references is found on main image page in Commons: Commons:File:Metastasis sites for common cancers.svg#Summary
- ^ Bacac, M; Stamenkovic, I (February 2008). "Metastatic cancer cell". Annual Review of Pathology 3: 221–47. doi:10.1146/annurev.pathmechdis.3.121806.151523. PMID 18233952.
- ^ http://www.springerlink.com/content/v8wt2q033u674121/
- ^ Robert Weinberg, The Biology of Cancer, cited in Basics: A mutinous group of cells on a greedy, destructive task, by Natalie Angier, New York Times, 3 April 2007
- ^ a b Briasoulis E, Pavlidis N (1997). "Cancer of Unknown Primary Origin". Oncologist 2 (3): 142–152. PMID 10388044. http://theoncologist.alphamedpress.org/cgi/pmidlookup?view=long&pmid=10388044.
- ^ Poste G, Fidler IJ (January 1980). "The pathogenesis of cancer metastasis". Nature 283 (5743): 139–46. doi:10.1038/283139a0. PMID 6985715.
- ^ a b c d e f Ramaswamy S, Ross KN, Lander ES, Golub TR (January 2003). "A molecular signature of metastasis in primary solid tumors". Nature Genetics 33 (1): 49–54. doi:10.1038/ng1060. PMID 12469122.
- ^ van 't Veer LJ, Dai H, van de Vijver MJ, et al. (January 2002). "Gene expression profiling predicts clinical outcome of breast cancer". Nature 415 (6871): 530–6. doi:10.1038/415530a. PMID 11823860.
External links
Medical information about metastatic cancer
- Q&A: Metastatic Cancer – from the National Cancer Institute
- Invasion and Metastases – from Cancer Medicine e.5
- How Cancer Grows and Spreads – an interactive Flash presentation that explores the progression of a carcinoma from a single cell to metastasis; from Children's Hospital Boston
Charities and advocacy groups dealing with metastatic cancer
- The MetaCancer Foundation – resources and support for metastatic cancer survivors and their caregivers
- Metastatic Breast Cancer Network
- Children's Cancer Research Charity for Metastatic Cancer in Kids
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Pathology: Tumor, Neoplasm, Cancer, and Oncology (C00–D48, 140–239)
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