What is cancer and how does it develop?

What is cancer?

The term cancer encompasses a large group of diseases that are characterized by the development of abnormal cells, which divide, grow and spread uncontrollably anywhere in the body.

Normal cells divide and die for a programmed period of time. However, the cancer or tumor cell "loses" the ability to die and divides almost without limit (Figure 1). Such multiplication in the number of cells comes to form masses, called "tumors" or "neoplasms", which in their expansion can destroy and replace normal tissues.

Figure 1:

A. Normal cells are divided in a controlled manner. When a normal cell develops mutations or other alterations that can not be adequately repaired, it activates its own cell death program to control its development and growth. This process is known as "apoptosis".

B. Cancer cells develop mutations that are not repaired and lose the ability to die.

Some cancers may not form tumors, as they typically do in those of blood origin. On the other hand, not all tumors are "malignant" (cancerous). There are tumors that grow at a slow pace, that do not spread or infiltrate the tissues of the neighbors and are considered "benign."

The total number of new cases of cancer in Spain in 2015 was 247,771 (148,827 in men and 98,944 in women). The most frequently diagnosed cancer types in 2015 were colorectal (41,441 cases), prostate (33,370 cases), lung (28,347 cases), breast (27,747 cases) and bladder (21,093 cases).

In the last 20 years, the number of diagnosed tumors has experienced a constant growth in Spain due not only to the population increase, but also to the techniques of early detection and the increase in life expectancy (since the risk of developing tumors increases with the age).

Although the risk of developing cancer has increased, fortunately the risk of cancer mortality has been decreasing considerably in the last two decades. Despite the fact that around 50% of patients diagnosed with cancer in Spain live more than 5 years, those who suffer from advanced cancer usually have much shorter survivals. The behavior, prognosis and treatment of the different types of cancer, even within the different evolutionary phases of the same tumor, are very variable

How is it diagnosed and what does it look like?

Thanks to the techniques of population screening or screening every time they detect more tumors in early stages without giving rise to symptoms and therefore with much better results.

The manifestations derived from the presence of the tumor can be very varied, from a rapid growing growth, persistent cough or hoarseness or digestive bleeding. It should be remembered that the vast majority of these signs or symptoms are common with other diseases (milder in general). Therefore, depending on the symptoms, a certain type of tests will be carried out to carry out the diagnosis.

Generally, the differential diagnosis (assessing the possible causes of a symptom or sign) will begin with anamnesis (medical examination) and physical examination. Subsequently, it may require analytical investigations and some imaging tests such as radiography or scan. Sometimes the results may be suggestive of their existence, for example, discovering a mammary nodule on examination or a mammogram, a lung mass on an x-ray or an elevated tumor marker (Figure 2, A).

However, for a diagnosis of certainty, histological confirmation is essential, which is carried out by the pathologist analyzing the tumor through the microscope (Figure 2, B). For this purpose, a sample of the tumor tissue must always be extracted and analyzed, with procedures such as aspiration or biopsy.

Very exceptionally, as it can happen in some hepatocarcinomas or brain tumors, the pathological diagnosis can be dispensed with.