The PIK3CA gene has preliminary evidence supporting a correlation with autosomal dominant Cowden syndrome and Cowden-like syndrome (PMID: 23246288, 22729224, 24497998). The PIK3CA gene is associated with rare conditions where the pathogenic variant is constitutionally mosaic and not inherited (MedGen UID: 442876, 355421).
The PIK3CA gene is an oncogene involved in many complex and intricate intracellular signaling pathways, including the PI3K-AKT-mTOR network. This pathway plays an important role in the regulation of cell growth, proliferation, differentiation, motility, survival, metabolism, and protein synthesis.
Several studies have identified PIK3CA variants in individuals with characteristics similar to Cowden syndrome and/or Cowden-like syndrome (PMID: 23246288, 22729224, 24497998). However, the sample size and data are very limited and available evidence is insufficient to make a determination regarding this association at this time. Therefore, PIK3CA is considered a “preliminary-evidence” gene and is available on Invitae’s Breast Cancer Panel and Breast and Gyn Cancers Panel. Preliminary-evidence genes are selected from an extensive review of the literature and expert recommendations, but the association between the gene and the specific condition has not been completely established. This uncertainty may be resolved as new information becomes available, and therefore clinicians may continue to order these limited-evidence genes.
The PIK3CA gene is also associated with rare overgrowth and vascular malformation conditions where the pathogenic variant is constitutionally mosaic and not inherited (MedGen UID: 442876, 355421).
PIK3CA provides instructions for making the p110 alpha (p110α) protein, which is a catalytic subunit of the phosphatidylinositol 3-kinase (PI3K) enzyme. PI3K phosphorylates certain cell-signaling molecules involved in cell growth, proliferation, migration, and survival. PI3K also plays a role in the production of new proteins and transport of materials within cells. Studies suggest that PI3K signaling may be involved in the regulation of several hormones and may play a role in the maturation of adipocytes ( National Library of Medicine. Genetics Home Reference. PIK3CA.. Accessed March 2016).
Variants in PIK3CA have autosomal dominant inheritance. This means that an individual with such a variant has a 50% chance of passing that variant on to their offspring.
Because the evidence regarding PIK3CA and Cowden and Cowden-like syndrome is limited and preliminary, there are no guidelines or recommendations to suggest alteration to medical management based solely on the presence of an PIK3CA variant. However, an individual’s cancer risk and medical management are not determined by genetic test results alone. Overall cancer risk assessment incorporates additional factors including personal medical history, family history as well as available genetic information that may result in a personalized plan for cancer prevention and surveillance.
It is advantageous to know if a PIK3CA variant is present even though the the data regarding this gene is currently limited. At-risk relatives can be identified, allowing pursuit of a diagnostic evaluation. In addition, the available information regarding hereditary cancer susceptibility genes is constantly evolving and clinically relevant PIK3CA data is likely to become available in the near future. Awareness of this variant allows patients and their providers to be vigilant in maintaining close and regular contact with their local genetics clinic in anticipation of new information, inform at-risk family members, and diligently follow standard screening protocols.
Review date: March 2016
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Our sequence analysis covers clinically important regions of each gene, including coding exons, +/- 10 base pairs of adjacent intronic sequence, and select noncoding variants. Our assay provides a Q30 quality-adjusted mean coverage depth of 350x (50x minimum, or supplemented with additional analysis). Variants classified as pathogenic or likely pathogenic are confirmed with orthogonal methods, except individual variants that have high quality scores and previously validated in at least ten unrelated samples.
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