Metastases are secondary malignant tumors of various organs and tissues that have arisen as a result of hematogenic, lymphogenic or implantation spread of malignant cells of the primary neoplasm. They can be found in any organ. In the early stages, they are asymptomatic. Subsequently, clinical manifestations depend on the localization of metastasis. The diagnosis is made taking into account anamnesis, complaints, objective examination data, test results and instrumental studies. Treatment – chemotherapy, radiotherapy, surgical interventions.
Meaning
Metastases are distant foci of the oncological process that have arisen during the movement of malignant cells through the body. They are detected in people of all ages, but the greatest number of lesions are found in patients older than 50 years. They can appear in most malignant tumors and affect any organs. Most often, malignant neoplasms metastasize to the lymph nodes, lungs and liver. Metastases to the bones, adrenal glands, kidneys and central nervous system are somewhat less common. Metastatic lesions of the pancreas, spleen, skin, skeletal muscles and heart muscle are rarely diagnosed.
Disorders of the function of various organs caused by the growth of metastases are the leading cause of mortality in oncological diseases. The appearance of secondary foci worsens the prognosis and makes radical treatment of a malignant tumor impossible or creates significant limitations in the choice of therapy methods. Diagnosis and treatment of metastases are carried out by specialists in the field of oncology and other specialties (depending on the localization of the secondary focus).
Etiology and pathogenesis
Without appropriate treatment, metastases occur over time in almost all malignant tumors, but the timing of their appearance can vary significantly. Sometimes metastases are detected several years after the development of the primary process, sometimes after several months, and sometimes they become the first manifestation of cancer, so the time interval between the development of the primary tumor and the occurrence of metastases cannot be established even approximately.
Experts believe that in some cases, malignant cells can migrate to various organs, forming “dormant foci”, which subsequently become active and begin to grow rapidly. However, the reasons why metastases in the same disease appear and develop at different rates have not yet been established. We can only list a number of factors contributing to the rapid emergence and progression of secondary formations.
Such factors include a large number of small vessels around the primary neoplasm, the location and histological structure of the primary focus, immune disorders and the age of patients (metastases occur and progress faster in young people than in the elderly). Antitumor therapy is of great importance – after such therapy it is difficult to predict the probability and possible time of the appearance of metastases. Sometimes secondary foci occur several years after the course of treatment, against the background of changes in some living conditions or for no apparent reason.
Primary tumor cells can spread through the body in three ways: lymphogenic (through lymphatic vessels), hematogenic (through blood vessels) and implantation. Implantation metastasis becomes possible after the destruction of the organ capsule and the release of malignant cells into one or another natural cavity. For example, ovarian cancer cells can migrate to the surface of the liver through the abdominal cavity, and primary lung cancer cells can migrate to the surface of the pleura through the pleural cavity.
The predominant pathway of metastasis is determined by the origin and degree of malignancy of the tumor. The cells of connective tissue and epithelial neoplasms migrate more often along the lymphatic pathways. With tumors of a high degree of malignancy, hematogenic spread prevails. In most cases, lymphogenic metastases appear earlier than hematogenic ones. First of all, regional lymph nodes suffer. Then the malignant cells can spread further through the lymphatic system.
Knowledge of the features of lymph flow in a particular anatomical zone allows you to determine possible ways of metastasis and identify secondary clusters of malignant cells (except in cases of micrometastasis). Hematogenous metastases occur at a considerable distance from the organ affected by the primary process, therefore, in order to detect them, it is necessary to conduct a comprehensive examination taking into account the most likely areas of metastasis.
Different types of cancer metastasize to various organs with different frequency. Thus, breast cancer, kidney cancer, prostate cancer and thyroid cancer most often metastasize to the lungs, bones and liver. Stomach cancer, ovarian cancer, colon cancer, uterine body cancer and pancreatic cancer affect the liver, peritoneum and lungs. Rectal cancer and lung cancer spread to the liver, adrenal glands and lungs (with lung cancer, the second lung suffers). Melanoma metastases to the liver, lungs, skin and muscles.
Among secondary neoplasms, solid nodular forms prevail, ulcerative surfaces (for example, with skin lesions), mucus-forming volumetric formations (Krukenberg metastases) and other types of tumors are less common. The size of metastases can vary from a few millimeters to 20 centimeters or more. There may be a single lesion of a certain organ, multiple lesions of a certain organ, as well as single or multiple secondary foci in several organs. Separately, it is worth mentioning the so–called “dust” metastases – multiple small foci in the abdominal cavity, provoking the development of ascites.
According to their histological structure, secondary neoplasms usually correspond to the primary tumor. However, in some cases, metastases may have a histological structure that differs from the structure of the primary cancer. Usually, such differences are detected when a tumor of a hollow organ metastasizes into a parenchymal organ (for example, with metastatic liver cancer resulting from primary colon cancer). Sometimes, due to differences in the structure of primary and secondary foci, difficulties arise in differentiating metastases and multiple cancers.
Symptoms
In the initial stages, metastases are usually asymptomatic. Subsequently, clinical manifestations depend on the localization of the secondary neoplasm. Local symptoms are combined with common signs of cancer: hyperthermia, loss of appetite, weight loss up to cancerous cachexia, general weakness and anemia. With metastases to the lymph nodes, there is an increase in their size, determined by palpation or during visual examination.
Nodes are usually painless, of a soft-elastic consistency. Most often, metastases are localized in the cervical, inguinal, axillary and supraclavicular lymph nodes. With a sufficiently large size, such foci can be detected already at the stage of a routine examination. Detection of metastases in some lymph nodes (retroperitoneal, paraaortic, abdominal nodes, mediastinal nodes) is possible only during instrumental studies, since these anatomical formations are not available for objective examination. Suspicion of the presence of such metastases may arise with their significant increase, causing compression of nearby anatomical formations.
The manifestations of hematogenous metastases are determined by their localization. With secondary foci in the brain, dizziness, bursting headaches, nausea, vomiting and focal neurological disorders occur. With metastasis to the spinal cord, there are pains, rapid fatigue with physical exertion, disorders of the pelvic organs, progressive disorders of movement and sensitivity. With metastases in the lungs, there are frequent relapses of inflammatory diseases (bronchitis, pneumonia, influenza, ARVI), followed by shortness of breath and cough with an admixture of blood in the sputum.
Liver metastases are manifested by heaviness and pain in the right hypochondrium, violation of hepatic functions, enlargement and tuberosity of the liver. In the later stages, jaundice, ascites and progressive liver failure are detected. Secondary neoplasms in the bones cause excruciating pain, hypercalcemia and pathological fractures. Compression of the spinal cord, nerve and vascular trunks is possible. With metastases to the peritoneum, ascites occurs due to a violation of the regulation of the process of excretion and absorption of fluid by the tissues of the peritoneum.
Skin metastases are dense, rapidly growing single or multiple nodes of a solid, bluish or pinkish color. Subsequently, their decay and ulceration are observed. In some primary neoplasms (for example, breast carcinoma, colon cancer, ovarian cancer and bladder cancer), the symptoms of secondary skin tumors can mimic the clinical picture of erysipelas. Less often (usually with breast tumors), scleroderm–like metastases are detected.
Diagnostics
The diagnosis is established on the basis of clinical data and the results of additional studies. Due to the high propensity to develop metastases, any malignant neoplasm is an indication for an extended examination (even if there are no signs of damage to other organs). Patients with suspected metastases are prescribed a general blood test, a biochemical blood test and a blood test for cancer markers. Patients are referred for chest X-ray, abdominal ultrasound, pelvic ultrasound, CT and MRI of the brain, CT and MRI of the spinal cord, skeletal scintigraphy, radiography of skeletal bones and other studies.
The presence of metastases is finally confirmed during histological or cytological examination of the altered tissue. The collection of histological material from soft tissues is carried out by incision, core or pinch biopsy. With a superficial location of metastases, scarification biopsy is used, with bone damage – trepan biopsy. The material for cytological examination is obtained by taking ordinary prints or smears-prints. An aspiration biopsy is performed to take the fluid.
Differential diagnosis of metastases is carried out with primary neoplasms and with multiple cancers (with simultaneous or almost simultaneous detection of several foci in one or different organs). In some cases, differentiation with degenerative-dystrophic and inflammatory processes is required. Thus, symptomatic pneumonia with metastases in the lungs must be differentiated from ordinary pneumonia, small metastases in the spine against the background of previous osteoporosis – with age-related changes in the spine, etc.
Treatment
Treatment tactics are determined individually, taking into account the type of cancer, the state of the primary tumor, the general condition of the patient, the sensitivity of cells to a particular type of therapeutic effect, the number, localization and size of metastases. It is possible to use radiotherapy, chemotherapy, immunochemotherapy, hormone therapy, classical surgical interventions, radiosurgery, cryosurgery and embolization of feeding arteries. As a rule, a combination of several treatment methods is used for metastases (for example, chemotherapy and radiation therapy, chemotherapy and immunotherapy, radiation therapy and surgery, etc.). Indications for surgical treatment and the scope of intervention also depend on the number and localization of metastases.
With metastases to regional lymph nodes, lymphadenectomy is usually performed in combination with the removal of the primary neoplasm. With controlled primary tumors and single metastases to distant organs, radical excision of secondary foci is possible in some cases. In case of multiple metastases, surgical intervention is usually not indicated. The exceptions are situations when palliative surgery can delay the death or improve the quality of life of the patient (for example, craniotomy to reduce dangerous intracranial pressure caused by a metastatic brain tumor).
Forecast
Until recently, the presence of metastases was considered as evidence of the imminent death of the patient. Now the situation is gradually changing, although the presence of secondary tumors is still considered as an extremely unfavorable prognostic sign. The use of new methods of diagnosis and treatment in some cases can increase the average life expectancy of patients. Under certain conditions, radical treatment of metastases of some localizations became possible, for example, single foci of metastatic liver cancer or metastatic brain cancer.
In general, the prognosis for metastases is determined by the degree of neglect of the oncological process, the capabilities of a particular medical institution (some therapeutic and diagnostic methods are available only in large centers), the type, localization and stage of the primary tumor, the patient’s age, the state of his immune system, the degree of exhaustion, the level of dysfunction of various organs, etc. The average life expectancy for metastatic liver cancer is about six months, for brain damage – several weeks, for bone metastases – several years, for secondary neoplasms in the kidneys – 1-3 years.
