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Novel Genetic Mutations Discovered in Two Benign Bone Tumors

Posted Nov 04 2013 12:00am

All readers of this blog should now be familiar with how genomic analysis of malignant tumors can provide information about their prognosis and the best treatment choices. For the most part and with exceptions like the Philadelphia chromosome , genomic testing hasn't provided much help in tumor diagnosis up to now. A recent article on the web discussed how two genetic errors have been linked to chondroblastoma and giant cell tumor of bone (see: Novel Mutations Define Two Types of Bone Tumor: Two Related Genes Underlie the Development of Two Rare Bone Tumors in Nearly 100 Per Cent of Patients ). Below is an excerpt from the article:

Scientists have made a rare discovery that allows them to attribute two types of tumour almost entirely to specific mutations that lie in two related genes. These mutations are found in nearly 100 per cent of patients suffering from two rare bone tumours; chondroblastoma and giant cell tumour of the bone. Chondroblastoma and giant cell tumour of bone are benign bone tumours that primarily affect adolescents and young adults, respectively....Occasionally, these tumours can be difficult to differentiate from highly malignant bone cancers...[A Wellcome Trust Sanger Institute] team sequenced the full genomes of six chondroblastoma tumours and found that all six tumours had mutations in one of two related genes, H3F3A and H3F3B, which produce an identical protein, called histone 3.3. Extending the study to more chondroblastoma tumours and to other bone tumours, they were able to verify that this mutation was found in almost all cases of chondroblastoma. Interestingly, the team also observed that most cases of a different type of bone tumour, giant cell tumour of bone, have a mutation in the H3F3A gene, albeit in a different position in the gene. A pattern emerged where both tumour types, chondroblastoma and giant cell tumour of bone, are defined by specific histone 3.3 mutations.

Here's a brief description of the giant cell tumor of bone from the Wikipedia (see: Giant-cell tumor of bone ):

Giant-cell tumor of bone a relatively uncommon tumor of the bone. It is characterized by the presence of multinucleated giant cells (osteoclast-like cells). Malignancy in giant cell tumor is uncommon and occurs in approximately 2% of all cases. However, if malignant degeneration does occur it is likely to metastasize to the lungs. Giant cell tumors are normally benign,with unpredictable behavior. It is a heterogeneous tumor composed of three different cell populations. The giant-cell tumour stromal cells ...constitute the neoplastic cells, which are from an osteoblastic origin and are classified based on expression of osteoblast cell markers such as alkaline phosphatase and ostocalsin. In contrast, the mononuclear histiocytic cells and multinucleated giant cell fractions are secondarily recruited and comprise the non-neoplastic cell population. They are derived from an osteoclast-monocyte lineage....

With the rapid drop in the cost of next-generation-sequencing (NGS), specific genetic errors in various types of tumors will be described with increasing frequency although most of the common malignant lesions have multiple genetic errors. Some of these errors, as in the case of the two bone tumors discussed here, will be useful in their diagnostic workup by pathologists. In this way, genomic analysis may be accorded a similar status to, say, special stains. Equally likely, however, is that many tumors will be biopsied and their diagnosis determined very early in the course of the disease (see: Genetic errors identified in 12 major cancer types ). Here is an excerpt from this article relating to mutated genes in cancer:

Examining 12 major types of cancer, scientists at Washington University School of Medicine...have identified 127 repeatedly mutated genes that appear to drive the development and progression of a range of tumors in the body. The discovery sets the stage for devising new diagnostic tools and more personalized cancer treatments. The research, published Oct. 17 in Nature, shows that some of the same genes commonly mutated in certain cancers also occur in seemingly unrelated tumors. For example, a gene mutated in 25 percent of leukemia cases in the study also was found in tumors of the breast, rectum, head and neck, kidney, lung, ovary and uterus. Based on the findings, the researchers envision that a single test that surveys errors in a swath of cancer genes eventually could become part of the standard diagnostic workup for most cancers. Results of such testing could guide treatment decisions for patients based on the unique genetic signatures of their tumors. 

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