S2125 Short Time Recurrence of Retroperitoneal Desmoid Tumor in Patient With Familial Adenomatous Polyposis

Abstract

Introduction: A Desmoid Tumor (DT) is a locally invasive, non-metastatic mesenchymal stem cell tumor that typically manifests as a soft tissue mass occurring in muscles, fasciae and aponeuroses. We present a case of a patient with recurrence of a retroperitoneal DT shortly after resection. Case Description/Methods: A 34-year-old male presented with abdominal pain found to have a large (11 × 14.4 * 14 cm) intrabdominal mass. IR transcatheter biopsy of the mass confirmed DT. He underwent bidirectional endoscopy and found to have more than hundred adenomatous colon polyps. Genetic testing confirmed APC mutation. Patient was diagnosed with DT associate with Familial Adenomatous Polyposis (FAP). He underwent radical resection of mesenteric mass and small bowel (20 cm of terminal ileum), omentectomy as well as total colectomy with ileorectal anastomosis. There was no evidence of lymphoid involvement. About 3 months later, he was re-admitted for increased abdominal girth with abdominal pain. MRI scans demonstrated a new, extensive, lobulated soft tissue mass occupying the entire abdominal cavity measuring 23.4 × 12.5 × 24.2 cm. Biopsy of the mass confirmed recurrent DT. Given the large size and proximity to the superior mesenteric artery, the mass was deemed to be unresectable. Patient was initially started on palliative systemic treatment with liposomal Doxorubicin. Due to lack of response, he was then switched to weekly methotrexate and Vinblastine (Figure). Discussion: DTs are rare neoplasms, making up only 0.03% of all neoplasms and 3% of soft tissue tumors. They typically include the abdominal wall, extremities, and mesentery. Although the etiology of DTs is not well known, there are several risk factors that are associated with their occurrence. Genetic syndromes such as FAP and Gardner syndrome have a well-known association with DTs. Other associations include antecedent trauma to the site of the lesion, pregnancy, and female sex. Numerous studies have been done assessing the efficacy of surgery, radiotherapy, and chemotherapy in managing DTs. However, none have shown conclusive benefit. The recurrence rate, particularly following surgical management, has been found to be as high as 77%. Given the lack of definitive management and high recurrence rates, treatment options should likely include combination of both surgical intervention and systemic treatment after discussing options and adverse effects of treatment with the patient.Figure 1.: A, Contrast enhanced CT axial through the lower abdomen demonstrating recurrence of large mass now occupying the majority of the abdominal cavity (black star); B, Spindle cell lesion, with fascicular and loose storiform growth patterns (H&E, 40×) prior to resection; C, Recurrent tumor with pathology demonstrating spindle cell lesion with more edema and/or myxoid stroma.