Science Series #5: Solid Tumor
What is a solid tumor?
Solid tumors are an abnormal mass of tissue that usually does not contain cysts or liquid areas. These may be benign (not cancerous) or malignant (cancerous). Different types of solid tumors are named for the type of cells that form them. Examples of solid tumors are sarcomas, carcinomas, and lymphomas.
Not all tumors are cancer. However, the term solid tumor is used to distinguish between a localized mass of tissue and leukemia, which is a type of tumor that takes on the fluid properties of the organ it affects such as blood.
Solid tumors in children
Solid tumors make up about 30% of all pediatric cancers. The most common types of solid tumors in children include brain tumors (glioblastomas), neuroblastoma, rhabdomyosarcoma, Wilms’ tumor, and osteosarcoma. The types of cancers that develop in children are often different from the types that develop in adults. Unlike many cancers in adults, childhood cancers are not strongly linked to lifestyle or environmental risk factors. And only a small number of childhood cancers are caused by DNA (gene) changes that are passed from parents to their child.
(Source: Cancer.org and Kline et al. 2003)
Solid tumor diagnosis
With the sequence of the complete human genome, researchers have identified opportunities for detecting and defining molecular alterations in the germline, as well as within malignant tumors. Identification of mutations that drive both neoplastic transformation of normal tissue, as well as progression to more advanced disease states, provides insight into the biology of neoplasia and therapies to arrest the disease. The discovery of many somatic alterations in the tumor cell genomes, new forms of regulatory nucleic acids, gene expression profiling, whole exome sequencing, and microRNA profiling are a few of the molecular tests used by the clinical laboratory to support the individualized use of therapies and improve the outcomes of cancer patients.
Molecular biomarkers can be used to refer to nonimaging biomarkers that have biophysical properties, which allow them to be measured in biological samples, and include nucleic acid–based biomarkers such as gene mutations or polymorphisms and quantitative gene expression analysis, peptides, proteins, lipids metabolites, and other small molecules.
A number of molecular markers have been established for neuroblastoma risk assessment, some of which are currently in clinical use. Among others, these markers include amplification status of the proto-oncogene MYCN, copy number status of chromosomes 1p and 11q, ploidy of the tumor cells, and numerical and segmental copy number alterations. Furthermore, several other genetic alterations, such as activating ALK mutations, inactivating mutations of the ATRX gene, and rearrangements of the TERT locus, have been reported to impact clinical outcome.
As Glioblastomas are a malignant tumor at its maximum capacity, the accuracy of such tests is of utmost importance in correctly diagnosing patients. The major biomarkers studied in the field of Glioblastomas such as O6‐methylguanine‐DNA methyltransferase (MGMT), EGFR, PDGFRA and IDH are further discussed; although other relevant biomarkers such as NF1, VEGF, p16INK4A and many more harbor clinical significance.
(Source: Clinical and Laboratory Standards Institute)
Neuroblastomas and Glioblastomas
Neuroblastoma is the most common extracranial solid tumor of childhood, is thought to originate from undifferentiated neural crest cells. Amplification of the MYC family member, MYCN, is found in ∼25% of cases and correlates with high-risk disease and poor prognosis. Currently, amplification of MYCN remains the best-characterized genetic marker of risk in neuroblastoma.
- Neuroblastoma develops from nerve cells in the fetus called neuroblasts. Usually, as a fetus matures and after birth, the neuroblasts develop normally. Sometimes they become cancerous, causing neuroblastoma.
- Neuroblastoma can be inherited (passed down in families).
- Neuroblastoma tumors generally develop in the adrenal glands (located on top of the kidneys), where neuroblasts are most commonly found. But neuroblastoma can also begin in or spread to other areas including the chest, the spine or spinal cord regions and the abdomen.
Glioblastoma, also known as glioblastoma multiforme (GBM), is the most aggressive type of cancer that begins within the brain. Initially, signs and symptoms of glioblastoma are nonspecific. They may include headaches, personality changes, nausea and symptoms similar to those of a stroke. Symptoms often worsen rapidly and may progress to unconsciousness.
The cause of most cases of glioblastoma is not known. Uncommon risk factors include genetic disorders, such as neurofibromatosis and Li–Fraumeni syndrome, and previous radiation therapy.
MGMT promoter methylation is a strong prognostic biomarker in pediatric and adult patients with glioblastoma treated. Patients older than 65 years old with glioblastoma whose tumors lack MGMT promoter methylation, derive minimal benefit from such chemotherapy. Thus, MGMT promoter methylation status has become a frequently requested laboratory test in neuro-oncology.
(Source: St. Jude Children’s Research Hospital)
Treatment strategies for solid tumor
The best strategy for fighting cancer is prevention by making changes in life-styles to reduce cancer risk. Nevertheless, even if we were to apply all that we know about preventing cancer, one out of four cancers would still occur. Because of this, therapies that target malignancies after they have developed will continue to be important for some time to come. The most commonly used treatment modalities for cancer include some combination of surgery, radiation therapy, and chemotherapy. Newer forms of treatment continue to emerge.
(Source: University of Florida)
Doing Our Part
The Jacinto Convit World Organization (JCWO) supports a free of cost molecular diagnostics program for the control and survival of pediatric patients affected by various types of cancer, in poor developing countries. Through a strategic partnership with local NGOs, specialized tests are performed to detect the genes of MYCN for Neuroblastomas and MGMT for Glioblastomas. MYCN amplification is carried out in few places in the Latin American region, including private laboratories. Importantly, JCWO works in the expansion of the MDP to benefit other countries or regions that are poor, especially those with highly deficient public health systems.
To date, 2 genetic sequences based on these diagnostics are published in GenBank, a world reference sequence database of National Center for Biotechnology Information (NIH); contributing to scientific advances in solid tumors.