cancer's source (coughing up blood—"probably lung", urinating blood—"probably bladder"), complex imaging will not either. 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. in other cases, the tumor might just be too small and/or in an unusual location to be diagnosed. diagnosis pulmonary metastases shown on chest x-ray 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. 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. 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. 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." 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. recent work identified a form of genetic instability in cancer called chromosome instability (cin) as a driver of metastasis. in aggressive cancer cells, loose dna fragments from unstable chromosomes spill in the cytosol leading to the chronic activation of innate immune pathways, which are hijacked by cancer cells to spread to distant organs. 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. 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. 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, identifying the genes whose expression is changed in metastasis offers potential targets to inhibit metastasis. cut surface of a humerus sawn lengthwise, showing a large cancerous metastasis (the whitish tumor between the head and the shaft of the bone) micrograph of thyroid cancer (papillary thyroid carcinoma) in a lymph node of the neck. h&e stain ct image of multiple liver metastases ct image of a lung metastasis metastasis proven by liver biopsy (tumor (adenocarcinoma)—lower two-thirds of image). h&e stain. metastatic cancer in the lungs metastases from the lungs to the brain metastases from the lungs to the pancreas 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 increases a patient's likelihood of death. some cancers—such as some forms of leukemia, a cancer of the blood, or malignancies in the brain—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 many 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. in patients diagnosed with cup it is often still possible to treat the disease even when the primary tumor cannot be located. current treatments are rarely able to cure metastatic cancer though some tumors, such as testicular cancer and thyroid cancer, are usually curable. palliative care, care aimed at improving the quality of life of people with major illness, has been recommended as part of management programs for metastasis. results from a systematic review of the literature on radiation therapy for brain metastases found that there is little evidence to inform comparative effectiveness and patient-centered outcomes on quality of life, functional status, and cognitive effects. research although metastasis is widely accepted to be the result of the tumor cells migration, there is a hypothesis saying that some metastases are the result of inflammatory processes by abnormal immune cells. the existence of metastatic cancers in the absence of primary tumors also suggests that metastasis is not always caused by malignant cells that leave primary tumors. the research done by sarna's team proved that heavily pigmented melanoma cells have young's modulus about 4.93, when in non-pigmented ones it was only 0.98. in another experiment they found that elasticity of melanoma cells is important for its metastasis and growth: non-pigmented tumors were bigger than pigmented and it was much easier for them to spread. they shown that there are both pigmented and non-pigmented cells in melanoma tumors, so that they can both be drug-resistant and metastatic. history the first physician to report the possibility of local metastasis from a primary cancerous source to nearby tissues was ibn sina. he described a case of breast cancer and metastatic condition in the canon of medicine. his hypothesis was based on clinical course of the patient. in march 2014 researchers discovered the oldest complete example of a human with metastatic cancer. the tumors had developed in a 3,000-year-old skeleton found in 2013 in a tomb in sudan dating back to 1200 bc. the skeleton was analyzed using radiography and a scanning electron microscope. these findings were published in the public library of science journal. etymology metastasis is a greek word meaning "displacement", from μετά, meta, "next", and στάσις, stasis, "placement".