Cousins not twins: intratumoural and intertumoural heterogeneity in syndromic neuroendocrine tumours

Aidan Flynn, Trisha Dwight, Diana Benn, Siddhartha Deb, Andrew J Colebatch, Stephen Fox, Jessica Harris, Emma L Duncan, Bruce Robinson, Annette Hogg, Jason Ellul, Henry To, Cuong Duong, Julie A Miller, Christopher Yates, Paul James, Alison Trainer, Anthony J Gill, Roderick Clifton‐Bligh, Rodney J Hicks, Richard W Tothill

Hereditary endocrine neoplasias, including phaeochromocytoma/paraganglioma and medullary thyroid cancer, are caused by autosomal dominant mutations in several familial cancer genes. A common feature of these diseases is the presentation of multiple primary tumours, or multifocal disease representing independent tumour clones that have arisen from the same initiating genetic lesion, but have undergone independent clonal evolution. Such tumours provide an opportunity to discover common co-operative changes required for tumorigenesis, while controlling for the genetic background of the individual. We performed genomic analysis of synchronous and metachronous tumours from five patients bearing germline mutations in the genes SDHB, RET and MAX. Using whole exome sequencing and high-density SNP arrays, we analyzed two to four primary tumours from each patient. We also applied multi-regional sampling, to assess intra-tumoral heterogeneity and clonal evolution, in two cases involving phaeochromocytoma/paraganglioma and medullary thyroid cancer, respectively. Heterogeneous patterns of genomic change existed between synchronous or metachronous tumours, with evidence of branching evolution. We observed striking examples of evolutionary convergence involving the same rare somatic copy-number events in synchronous primary phaeochromocytoma/paraganglioma. Convergent events also occurred during clonal evolution of metastatic medullary thyroid cancer. These observations suggest that genetic or epigenetic changes acquired early within precursor cells, or pre-existing within the genetic background of the individual, create contingencies that determine the evolutionary trajectory of the tumour.