Gardner syndrome with a giant mass in the thoracic cavity: a case report and analysis of the related complications.

Gardner syndrome (GS) is a form of familial adenomatous polyposis (FAP) and is characterized by colonic polyposis, osteomas, and soft-tissue tumors. Desmoid tumors (DT) are lesions of mesenchymal origin and are an extra-colonic manifestation of GS. Gardner-associated fibroma (GAF) is considered to be a benign soft-tissue lesion related to DT and FAP. Here we present a case of an 18-year-old female patient with a huge lump in her right thoracic cavity and another lump located in her left lumbar muscles who was diagnosed with GS through a colonoscopy and through gene mutation detection. The patient underwent a surgical resection of the right thoracic tumor. Three months later, the left waist lump underwent medical treatment with tamoxifen and celecoxib and was monitored using computed tomography (CT). Subsequently, colonoscopy screening was performed annually to prevent colorectal cancer. GAF is frequent in GS, and such a huge GAP in the thorax is very rare, with few cases reported in the literature. Patients with GS must be closely monitored, and clinical and imaging examinations must be performed to detect any signs of tumors.