Let’s imagine that all of our body’s cells are like an enormous orchestra, where every group of cells (instruments) has a specific function (score) and only the organised interaction of all components (composer, conductor and musicians) can ensure the body’s healthy existence and functionality (harmony).
The function of each group of cells, regardless of its own vital importance, is subordinate to one single goal – the healthy functioning of the entire body. Unfortunately, the same cannot be said of cancer cells, whose main goals are to care for their own well-being and to survive, paying no mind to the regulatory mechanisms of the body or its tissues. Once they have mastered this egotistical ability for self-preservation, they continue to grow and multiply autonomously, over time disrupting the body’s internal structural and functional order and, in the end, leading to the body’s destruction.
Therefore, malignant tumours are a varied group of many different illnesses, which have one common characteristic – the ability to pathologically stimulate uncontrolled growth in cells.
Are all cancers malignant?
In everyday conversation, all malignant tumours are usually called cancers – breast cancer, leukaemia, lymph node cancer and others, but in reality they represent over 200 different diseases with varying courses, treatments and prognoses. Therefore, even one type of cancer, breast cancer for example, can differ significantly not only between patients, but even between tumours within the same patient and in later metastases in different tissues and organs. The prognosis will depend not only on the organic characteristics of the tumour, but also on the host body’s proper functioning and how it reacts to the illness. Current methods allow us to more precisely determine the tumour’s morphological, biological, genetic, molecular, epigenetic and other unique characteristics, which will largely account for the tumour’s behaviour and reaction to therapy. But everything is based on the atypical, cancer-specific cell and tissue changes, which allow us to reach a diagnosis. Therefore, a cancer diagnosis is determined only by testing tissue samples under the microscope and detecting these unique characteristics. New methods to discover cancerous tissues have also been devised, such as immunohistochemical methods. Although currently not part of routine testing, there are methods that can detect cells which have peeled away from the tumour, their DNA or even smaller particles in the blood. This is called a liquid biopsy, which will have a large role in future tumour diagnostics and treatment. However, in the meantime a cancer diagnosis is determined solely by cytological (on the cellular level) or morphological (in the tissue) verification. Although they can detect the possible presence of cancer, no medical imaging diagnostic method (X-ray, CT, PET/CT, MRI) can positively prove a diagnosis of cancer.
All malignant cancers can be classified by a variety of methods that differ from one another in their complexity. But to simplify this task, all types of cancers can be grouped according to their histological structure.
Carcinomas account for 80-90% of all malignant tumours. They develop from a variety of cells that cover the outer and inner surfaces of organs (epithelial tissue). It would be correct to apply the colloquially accepted term cancer only to these tumours. Furthermore, all carcinomas can be divided into two large subgroups – adenocarcinomas, which develop in the cells of the glandular epithelium (various secretion producers), and squamous cell carcinomas, which develop on the surface of the skin lining of hollow organs in the body and which line the respiratory and digestive tracts. In Latvia, these are also the most commonly occurring – skin, breast, prostate, intestinal and lung cancer. Rarer and more morphologically nuanced types can also be found. The course of the carcinoma and the prognosis of the disease can vary by leaps and bounds, from slow-growing types (so-called in situ or non-invasive cancers) to aggressive, fast progressing tumours that are difficult to control. Furthermore, this isn’t dependent on the tumour itself, but on a variety of lucky or unlucky coincidences, including the patient’s immune system, other illnesses, a patient’s state of mind and other factors.
Sarcomas are tumours that develop from connective tissues and supporting tissues – bone, cartilage, adipose tissue, elastic or fibrous connective tissue and muscle tissue. These account for 6% of all malignant tumours. Because sarcomas are usually similar in appearance to their original tissues, their names are also derived from their Latin designations – osteosarcoma (from bone tissue), chondrosarcoma (from cartilage), leiomyosarcoma (from smooth muscle tissue), rhabdomyosarcoma (from the muscle tissue of the skeleton), angiosarcoma (from blood vessel tissue), liposarcoma (from adipose tissue), mesotheliomas, gliomas, astrocytomas, myxosarcomas and others. Sarcomas are known to grow swiftly and to spread to the most distant tissues and organs. It’s not uncommon for the disease to have already metastasised by the time a diagnosis has been made, meaning that only systemic drug therapy can be applied (drugs are introduced into the blood and lymph nodes so they can spread throughout the entire body). By changing the therapy strategy, for example beginning treatment with drug therapy and performing an operation only afterward, it’s possible, in many cases, to overcome the illness or at least prevent its progression for a period of time. In any event, today we can achieve long lasting remission and significantly prolong the lives of patients suffering from sarcomas, despite their aggressive and difficult natures.
Lymphomas are tumours of the lymphatic system that affect the lymph nodes, spleen and other lymphatic tissue (tonsils, thymus). It’s not uncommon for lymphomas to develop in the stomach, breasts and in the brain. These are then called extranodal lymphomas (growing outside the lymph nodes). In general, all lymphomas are divided into two groups – Hodgkin disease and non-Hodgkin lymphoma. Immunohistochemical examinations, which allow these diseases to be divided into subgroups to find the most suitable course of therapy, are very important in the diagnosis of lymphoma. Although there are lymphoma patients who suffer from aggressive forms of this disease, today the majority of patients can be effectively treated achieving long-lasting remission and a significant prolonging of life. In Latvia, lymphomas are traditionally treated by haematologists, who have the most experience in detecting, treating and dynamically observing this disease.
Leukaemia, or blood cancer, is a malignant tumour of the bone marrow, characterised by the passage of immature and functionally inadequate blood cells into the surrounding blood. There are a number of different types that depend on the origin of the cells and they include myeloid leukaemia, lymphocytic leukaemia and erythrocytosis. Leukaemia is further classified as acute or chronic according to the characteristics of the cells. Targeted therapy (drugs that are attracted to very specific cell surface receptors or proteins) is often called personalised treatment, as this method of therapy is administered to patients who have cells with specific characteristics that have already been identified. Until now the largest advancement in personalised medicine has been imatinib (Glivec®), which is used to treat chronic myeloid leukaemia (CML). If its diagnosis was a death sentence in the 1980s, since the mid-1990s the average life expectancy for a patient being treated with imatinib is no longer measured in months, but in years and perhaps even decades. People with this specific genetic defect finally have real hope of recovery. New and effective drugs have also been created for other types of leukaemia, which give us hope that better results will be achieved in the future, especially a significant prolonging of life.
Myeloma develops from the plasma cells in bone marrow that secrete a unique protein, which can be detected in the blood. This disease is difficult to control, but a new generation of drugs could also prolong and improve the quality of life for these patients. Examples include adenosquamous carcinoma (from glandular epithelial cells and flat epithelial cells), teratocarcinoma, mixed mesodermal tumours, carcinosarcomas and others. A treatment plan is based on the dominant type of cells found in the tumour and that could include surgery, radiation and drug therapy.
Rare tumours account for roughly 4% of all cancers. The European Union considers a disease to be a rare cancer diagnosis (RARECARE definition) if it occurs in less than 6 cases for every 100,000 people. Globally speaking, many different malignant tumours belong to this category including various adenocarcinomas or unique forms of flat (squamous) cell tumours (intestinal adenocarcinomas, mucoepidermoid carcinomas, adenosquamous carcinomas, medullary adenocarcinomas, mucinous cystadenocarcinomas, verrucous carcinoma, etc.), ocular and mucous membrane melanomas, skin appendage tumours, embryomas, extragonadal germ cell tumours, rare soft tissue sarcomas, gastrointestinal stromal tumours, Kaposi’s sarcoma and many other forms. You can read more about them at http://www.rarecare.eu/rarecancers/rarecancers.asp.
By definition, all of these diseases are malignant. However, how aggressive they will be, how well they will respond to therapy and their effect on life expectancy will be determined by many different circumstances.