Physicians classify cancer in two general categories—cancers of the blood and solid tumor cancers. As its name implies, solid tumors are solid masses devoid of fluids or cysts. Solid tumors can be either malignant or benign. Not only do solid tumors present differently than blood tumors, but they may also require a different treatment protocol.
Both types of cancer may be treated using chemotherapy and radiation therapy. However, solid tumors may be treated with surgery and some blood cancers, such as leukemia, may include stem therapy as part of the treatment protocol.
Solid tumors can develop in the muscles, bone, and organs of the body. Examples include mesothelioma, sarcomas, lymphomas, sarcomas as well as cancers of the breast, prostate, kidney, ovaries, pancreas, thyroid, and colon.
Additionally, secondary solid tumors can erupt as a consequence of treating blood cancers with radiation or chemotherapy. In fact, solid tumors present the second most common type of tumor following treatment in cancer survivors.
The way solid tumors are classified plays an important role in understanding the cancer’s pathology, determining the most important course of treatment, and evaluating the patient’s prognosis.
Solid tumors are classified using grades based on the abnormalities pathologists identify in tumor cells and how likely the tumor is to spread. Tumorous tissue that appears similar to the organization of normal, healthy cells and tissue and tends to proliferate relatively slowly are called “well-differentiated.” Fast-proliferating tumor cells that look abnormal and are devoid of normal tissue structures are known as “undifferentiated” or “poorly differentiated.” There are four general tumor grades:
- Pathologists typically classify tumors with cells that closely resemble normal cells and proliferate slowly as Grade 1 tumors.
- Grade 2 tumor cells have more abnormalities in their structure, have moderate cell differentiation and replicate faster than grade 1 tumors.
- Tumors classified as either grade 3 or “high grade” have poor cell tissue differentiation and spread more quickly than grade 1 and 2 tumors.
- Grade 4 tumors lack cell differentiation altogether and look starkly different from healthy cells and lower grade tumors.
While many cancers are classified using this system, it’s important to note that some solid tumor types are defined using other grading systems.
Related article: Complications of Solid Tumors and Treatment
For example, doctors may classify breast cancer on mitotic rate, degree of tumor activity in milk ducts (tubule formation), and the size and shape of the nuclei found in tumors cells (known as nuclear grade). Each of these three categories receive a score ranging from 1 to 3. A score of 1 indicates that tumor tissue more closely resembles healthy cells and tissue. A score of “3” indicates is associated with cells and tissue that have the most abnormal appearance. After assigning a score to each of the three categories, the values are then added together for a composite score that ranges from 3 to 9. The values fall into three different tumor classifications:
- Low grade or well-differentiated tumors receive a composite score of 3 to 5.
- Tumors identified as being intermediate grade or moderately differentiated range from 6 to 7 in scoring.
- And tumors receiving scores of 8 or 9 are identified as being poorly differentiated.
The oncology community uses the Gleason scoring system to grade prostate cancer the pathological results of prostate biopsy samples. The pathologist compares the appearance of the diseased tissue to the healthy tissue and assigns a score of 1 to 5 for the tissue. The abnormal tissue that appears most commonly in the tumor(s) is called the primary pattern, while the secondary pattern the next most frequent appearing tissue pattern.
The scores for the primary and secondary patterns are added together for a Gleason score—results of which fall into four categories:
- Gleason X means the pathologist could not determine the Gleason score.
- Gleason 2-6 is associated with well-differentiated tumorous tissue.
- A Gleason 7 score is used to define moderate differentiated tumorous tissue.
- Gleason 8-10 scores means that tumor tissue has poor differentiation or is undifferentiated altogether.
Tumor grade plays a higher degree of significance in customizing treatment and evaluating the patient’s prognosis in certain types of cancers such as cancers of the breast and prostate as well as primary brain tumors and soft tissue sarcoma.