Molecular profile of synchronous metastatic colon cancer and anaplastic thyroid cancer in a patient with Lynch Syndrome.

e22049 Background: Lynch Syndrome is an autosomal dominant disorder caused by either germline mutation in a DNA mismatch repair gene: MLH1, MSH2, MSH6, or PMS2, or epigenetic silencing of MSH2. The syndrome consists of early onset malignancies and multiplicity of cancers. Colonic malignancies predominate with the frequency and distribution of extracolonic cancers dictated by the mutated gene. Methods: A 54 year old man with a family history of Lynch Syndrome and a MSH6 mutation was found to have synchronous colonic adenocarcinomas on screening colonoscopy. Within weeks he presented with a rapidly enlarging anaplastic thyroid cancer (ATC). On PET/CT he was found to have liver metastases (biopsy confirmed as colonic) and pulmonary metastases (biopsy confirmed as ATC). Tumor tissue from his colon and thyroid was sent for FoundationOne analysis of 343 genes. Cell free circulating tumor DNA (CtDNA) was sequenced for 54 genes using Guardant360 technology with blood taken post-thyroidectomy. Results: FoundationO...