Analysis of germline variants in pediatric patients diagnosed with desmoid tumors and nuchal-type fibromas

Desmoid tumor (DT) is a fibroblastic proliferation arising in soft tissue characterized by localized infiltrative growth with an inability to metastasize but with a tendency to recurrence. Nuchal-type fibromas are benign soft tissue lesions that are usually developed in the posterior neck. The development of these neoplasms can be associated with a hereditary cancer predisposition syndrome, mainly familial adenomatous polyposis (FAP) syndrome caused by APC germline mutations. Gardner syndrome is a variant of FAP characterized by the presence of extracolonic manifestations including soft tissue tumors as DTs and nuchal-type fibromas. However, the development of these tumors could be associated with germline alterations in other genes related to colorectal cancer development. The objective of this study was to analyze germline variants in APC, MUTYH, POLD1 and POLE genes in five pediatric patients diagnosed with DTs or nuchal-type fibromas. We identified two pathogenic variants in the APC gene in two different patients diagnosed with nuchal-type fibroma and DTs and two variants of uncertain significance in POLD1 in two patients diagnosed with nuchal-type fibroma. Two patients had family history of colorectal cancer, however, only one of them showed an APC germline pathogenic variant. The analysis of germline variants and genetic counseling is essential for pediatric patients diagnosed with DTs or nuchal-type fibromas and their relatives.