Staging is a schematic, rigorous, and standardized way of describing how large a tumor is and how far it has spread from its original location. We talk about it through an in-depth analysis of the Airc experts.
The cancer cells they behave very differently from healthy cells. They grow and multiply uncontrollably, without ending their life cycle as and when they should. Thus they form a tumor mass which, unlike healthy tissue, grows without limits, without recognizing borders around itself. Furthermore, the cells of a tumor can detach and migrate from the initial mass, reaching other parts of the body through the lymphatic system or the bloodstream and giving rise to metastases.
The development and spread of a tumor can take quite a long time, in which the cells accumulate more and more alterations and gradually differentiate from their original ones. Staging helps determine at what stage of this process the tumor is, how large and how widespread it is; it therefore represents a fundamental aspect that allows the diagnosis to be defined, since both the prognosis of the disease and the most appropriate types of treatment to be administered may depend on these characteristics.
If the tumor is, for example, located in only one site and is small, local treatment such as surgery or radiation therapy may be curative. In cases where, on the other hand, it is extended to other sites, a local intervention is usually not enough and it may be necessary to resort to systemic treatments, capable of producing effects throughout the body, such as chemotherapy, hormonal therapy or other newer drug treatments (for example, targeted therapies or immunotherapy).
How is the stage of a tumor measured?
There are several ways clinicians describe the stage of a tumor. These are methods that evolve over time as knowledge of the disease grows and techniques for instrumental diagnostics improve.
Beyond differences and specificities, almost all staging systems detect:
- The size of the primary tumor;
- Metastatic involvement of lymph nodes, when cancer cells have migrated to lymph nodes via the lymphatic system;
- the presence (and number) of distant metastases, i.e. of tumor cells migrated through the blood from the primary site to other organs.
From the combination of these elements, a detailed description of the tumor and its extension can be obtained.
How to interpret staging?
In the medical record, the staging of a tumor is indicated by a sail composed mostly of letters and numbers, and also specific to the classification system used.
The most common is the so-called TNM system, acronym for “Tumor, Node, Metastasis”. Each letter is usually associated with a number.
The letter T refers to the size of the primary tumor and the scale ranges from 1, which identifies the smallest tumors, to 4 for the largest ones. There is also the acronym T0, when the primary tumor is not detectable.
The letter N indicates if the tumor is extended to the lymph nodes. It may be followed by a number ranging from 0 (no lymph nodes involved) to 3 (many lymph nodes involved). This parameter also serves to understand, in addition to the quantity of lymph nodes affected, some morphological characteristics of the tumor and the distance from the primary tumor.
The letter M, which stands for metastasis, can have a value of 0 (if the tumor has remained confined to its primary site) or 1 (when the tumor has spread to other parts of the body).
It is a simple but complex system, which can be integrated by adding further letters and relative numerical values.
In the case of the lung cancer, for example, it is not uncommon for the abbreviations M1a and M1b to be used to describe the presence of metastases. The first indicates that the metastases are present and localized only in the contralateral lung, while the second denotes that the metastases are spread to other areas of the body. In the case of colorectal cancer, M1 indicates metastasis in a single area (in addition to the primary tumor), while M1b indicates metastasis in two areas. For the initial stages of epithelial tumors, the acronym Tis (from the Latin on site) is used to indicate a carcinoma still contained within the epithelium, therefore not yet invasive and therefore potentially curable only with complete removal.
The TNM system is not the only one used in cancer staging. There are many others, but they are usually only used for specific types of cancers, such as brain or blood cancers.
From the combination of the three factors (T, N and M) and their numerical values, the stages of diffusion and development can also be identified: from zero, typical of carcinoma in situ, up to the fourth, when the tumor metastases have reached distant areas from the primary location.
What tests reveal the stage of a tumor?
Several tests may be needed to arrive at a reliable staging, including:
- the physical examination, which, together with the symptoms and an accurate anamnesis, can provide the first indications on the site of the primary tumour;
- diagnostic imaging tests, including ultrasound, radiography, CT, magnetic resonance imaging (MRI), PET. These are methods that make it possible to detect the extent of the tumor and possibly the presence of secondary localizations;
- laboratory tests can provide indications on how the tumor is affecting the normal functioning of the organs;
- percutaneous biopsies (in some cases under instrumental ultrasound or CT control) and endoscopic biopsies allow the removal of a small sample of tissue to be subjected to microscopic analysis. Generally they allow to establish the nature of the tumor through cyto-histological analysis and to verify the possible extension to other tissues. Sometimes, due to the difficulty in locating the tumor site, a surgical biopsy can be used.
Are stage and rank the same thing?
The stage of a tumor is different from its grade. The former tells how big a cancer is and how far it has spread in the body, while the latter describes how abnormal the characteristics of the cancer cells are. The higher the degree, the more cancer cells are different from healthy ones and are destined to grow and spread rapidly in the body. Along with staging, the grade of a tumor can help determine prognosis and treatments. To find out the grade of the tumor, a sample is taken during a biopsy and viewed under a microscope.
There are different classification systems to define the grade of a tumor, which can vary from one type of tumor to another. In general, a scale of 1 to 4 is used depending on the amount of abnormalities present in the tumor cells.
Grade 1 tumors, also referred to as low-grade or well-differentiated, have cells that closely resemble healthy cells and tend to grow slowly. In grade 4 tumors, also called high-grade or undifferentiated, the cells differ greatly in morphological characteristics from those of normal tissues and tend to grow and spread rapidly.
Over the years, the histological characterization defined by the grade or by some specific classifications for each disease (for example the Gleason score, a parameter that indicates the aggressiveness in prostate cancer), have been added molecular and genetic specifications that allow to better distinguish tumors apparently similar, and which allow them to be addressed in a more targeted way.
Nurse Times editorial team
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