A case report of desmoid tumour—a forgotten aspect of FAP?

INTRODUCTION: Desmoid tumours are locally aggressive tumours which are common in Familial Adenomatous Polyposis (FAP). PRESENTATION OF CASE: A 20-year old Familial Adenomatous Polyposis (FAP) patient presented with abdominal pain and distention. Abdominal imaging showed small bowel obstruction and hydronephrosis due to a pelvic mass. This mass showed significant enlargement on repeat imaging, and a diagnostic biopsy confirmed desmoid tumour. The mass was deemed unresectable and he was initially started on sulindac and raloxifene. Repeat imaging however showed further enlargement of the tumour, and therefore vinblastine + methotrexate chemotherapy was commenced, with a good response. DISCUSSION: FAP is an autosomal dominant condition caused by a germline mutation in the adenomatous polyposis coli (APC) gene. Gardner’s syndrome is also caused by a mutation in the APC gene, and is now considered a different phenotypic presentation of FAP. Desmoid tumours are initially kept under observation while their size remains stable. Treatment options for enlarging desmoids tumours include surgery (first-line), radiotherapy, and systemic therapy with non-cytotoxic and cytotoxic therapy. CONCLUSION: FAP patients should be examined regularly post-panprocotocolectomy, since desmoid tumours may arise. The presence of epidermal cysts in this FAP patient suggests a diagnosis of Gardner’s syndrome.