CT imaging features of abdominal (mesenteric) desmoid tumour

A 38-year-old male patient presented with complains of dull aching upper abdominal pain since 1 month, few episodes of vomiting since 20 days, low-grade fever since 15 days. No history of trauma, weight loss or similar symptoms in past. Palpable minimally tender mass is noted within left-upper quadrant on examination. Blood count shows mild leukocytosis. Rest of the investigations are within normal limits. CECT abdomen and Upper gastrointestinal endoscopy were advised.

Contrast enhanced CT scan of abdomen shows well-defined rounded-oval fluid attenuating mass lesion within greater omentum with hyperdense mass-like anterior solid wall thickening. No areas of calcifications or internal haemorrhages. Contrast study shows nodular heterogenous enhancement within solid anterior mass-like thickening. Anteriorly, It is closely lying (almost inseparable) to greater curvature of stomach causing mild compression and displacement. No obvious gastric intraluminal growth is seen. Posteriorly, it closely abuts distal body of pancreas without obvious parenchymal infiltration. Minimal perilesional free fluid is noted. No obvious vascular encasement, bowel loops infiltration or visceral solid organ infiltration. Not any similar lesions are observed within abdomen and pelvis. Upper gastrointestinal endoscopy is unremarkable.

Desmoid tumours are benign, non-inflammatory fibroblastic with a tendency for local invasion but without metastasis. They are rare tumours, thought to account for only 0.03% of all neoplasms [6]. Desmoid tumours are found in all age groups but are most frequently encountered between 20 and 40 years of age. They are seen more in women (2:1). Abdominal desmoid can arise from musculature of abdominal wall, mesentery, retroperitoneum [1]. Mesenteric desmoid is rare and commonly seen in patients of familial adenomatous polyposis (F.A.P). Majority of patients with mesenteric desmoid have previous history of abdominal surgery [1]. Clinical presentation includes subacute to chronic abdominal pain, palpable abdominal mass, tenderness with or without fever or weight loss, vomiting, bowel obstruction.

Typical imaging features: Ultrasound is initial imaging modality. Tumours appear solitary or multiple well defined homogeneously or heterogeneously hypoechoic solid mass lesions with or without internal vascularity or bowel dilatation [2]. Contrast enhanced CT scan is imaging modality of choice to see for extent of lesion and adjacent organ/ bowel infiltration, for surgical planning as well as prognosis prediction [1]. Tumours appear in variable density, well-defined or ill-defined, homogenously / heterogeneously enhancing soft tissue solid or solid-cystic mass lesions within abdominal wall musculature, mesentery with-or without bowel infiltration. Mass-like enhancing infiltrative omental thickening, radiating fibrous strands into surrounding mesenteric fat are also typical CT imaging appearance [1,2]. MRI study helps to characterise lesions morphology due to better soft tissue contrast, mainly in abdominal and extra-abdominal location. MRI imaging can tell proportion of collagen fibers, spindle cells, and extracellular matrix present within the tumour based on variable signal changes in different sequences.  Tumours appear hypointense on T1W and hypo-or hyperintense on T2W images. Decreased signal-intensities on T2W images reflect dense collagen fibres and hypo-cellularity of tumour, whereas increased signal intensities on T2W images reflect presence of high spindle cells [3]. Tiny intra-lesional necrotic areas can be better identified in MRI imaging. Diffusion-weighted sequence of MRI imaging (DWI and ADC) is mainly useful to determine compact hyper-cellularity within tumour (as hyper-cellular tumours appear hypo-intense on ADC and hyper-intense on DWI images) [3]. PET-CT study has limited value, as tumours show low internal FDG uptake and metabolic activity.    

Diagnosis is generally confirmed by histopathological analysis of tumour tissue samples and immunohistochemical staining. Radiographically, mesenteric desmoid tumour mimics gastrointestinal stromal tumour (GIST) as both are positive for CD-117 marker. However, presence of CD-34 and beta catenin confirms the diagnosis of desmoid tumour [2].

Treatment includes surgical excision with negative surgical margins. Recurrence is high in case of aggressive tumours, multicentric disease or incompletely resected lesions. Chemotherapy can be given in such aggressive or recurrent lesions. Radiotherapy is generally not recommended as it increases the risk of enteritis [2].

Written informed patient consent has been obtained.