A blastoma is a type of cancer, more common in children, that is caused by malignancies in precursor cells, often called blasts. Examples are nephroblastoma, medulloblastoma and retinoblastoma. The suffix -blastoma is used to imply a tumor of primitive, incompletely differentiated (or precursor) cells, e.g., chondroblastoma is composed of cells resembling the precursor of chondrocytes.
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Molecular biology and treatment
Many types of blastoma have been linked to a mutation in tumor suppressor genes. For example, pleuropulmonary blastomas have been linked to a mutation of the coding for p53. However, the mutation which allows proliferation of incompletely differentiated cells can vary from patient to patient and a mutation can alter the prognosis. In the case of retinoblastoma, patients carry a visibly abnormal karyotype, with a loss of function mutation on a specific band of chromosome 13. This recessive deletion on the rb gene is also associated with other cancer types and must be present on both alleles, for a normal cell to progress towards malignancy. Thus, in the case of common blastomas, such as retinoblastomas, a practitioner may go directly into treatment, but in the case of rarer, more-genetically-linked blastomas, practitioners may karyotype the patient before proceeding with treatment.