Experts never tire of repeating that detect cancer early It is essential to improve the patient’s prognosis. Unfortunately, this is not always easy; some forms of this disease can take time to cause symptoms, and not all tests are quick to find them.
In fact, the way cancer is detected varies widely depending on the type of cancer in question and the patient’s own profile. In many cases, tumors are detected when a worrisome sign appears, prompting a clinical investigation. In others it can be found as part of a screening program (which is often a very positive thing, since it is possible that it occurs in the early stages when it has not yet caused symptoms. Other times, the positive for cancer is given as a collateral result of tests that were performed for any other reason.
Lab tests
Thus, for example, and as indicated by the National Cancer Institute of the United States, very high or very low concentrations in the blood of certain substances can be indicative of cancer. This, however, does not mean thate an abnormal test result implies the presence of a tumor; Normally, when what is considered a possible indication is detected, it is necessary to carry out specific analyzes in search of specific cancer markers.
As a curiosity, it should be noted that both healthy cells and cancer cells tend to produce substances considered as Tumor markers, only that the latter do so in much larger quantities. Therefore, in any case, professionals should interpret the results of the test.
imaging tests
On the other hand, certain imaging tests they can allow doctors to check for the presence of some types of tumor. These tests include some such as magnetic resonance imaging (MRI), computed tomography (CT), nuclear tomography, bone scintigraphy, positron emission tomography (PET), ultrasound or radiography.
The suitability of one or the other technique will depend to a great extent on the type of tumor and its location. Thus, a special case is that of colonoscopy, a test that combines imaging procedures (since an endoscope is inserted into the rectum) and biopsy, as we will see below.

biopsies
The biopsy is a test that consists of the extraction and analysis of samples of certain tissues. As such, and while it is not usually the first step in detecting a cancer, it tends to be an essential part of the process of confirming the presence of a tumor and determining its type and nature, as well as other important details in the treatment (microenvironment, mutations…).
Thus, there are frequent colonoscopy or bronchoscopy procedures, in which samples are obtained in the colon or bronchi respectively. In more serious cases, you can opt for biopsies through surgery, which also tries to remove as much tumor tissue as possible.
References
NIH. How cancer is diagnosed. National Cancer Institute. Consulted online at https://www.cancer.gov/espanol/cancer/diagnostico-estadificacion/diagnostico on 03/23/2023