Desmoid tumour of the abdominal wall

Clinical History

A 28-year-old pregnant woman at five months gestational age presented with a 4-month history of a painless mass in the left lower abdomen. The patient stated that the mass was gradually increasing in size.
On clinical admission, the mass was firm, nontender, and fixed to the left lower abdominal wall. Tumour markers were negative.

Imaging Findings

The transverse T1- weighted MR image shows the mass to be well-delineated with respect to the adjacent adipose tissue. The margin of the mass and the adjacent skeletal muscle is not well defined. The mass is predominantly isointense to muscle, with small areas of low signal intensity within it (Fig. 1). The transverse fat-saturated contrast material–enhanced MR image shows mild enhancement in the lateral and posterior aspects of the mass. The other parts of the mass show no enhancement (Fig. 2). The transverse fast spin-echo T2-weighted MR image also shows heterogeneous high signal, with low T2 signal intensity bands (Fig. 3).

Discussion

Desmoid tumours belong to a group of disorders called fibromatoses, which are characterized by fibroblastic proliferation, without evidence of inflammation or definite neoplasia.
The cause of most desmoid tumours is unknown and thus they are called sporadic. In the fertile age group, desmoid tumours are 1.8 times more common in female subjects than in male subjects. [1]
A well-known association occurs in patients with a past history of abdominal or pelvic surgery. Other associations include trauma, pregnancy, oestrogen therapy, familial adenomatous polyposis, and Gardner syndrome. [2]
In some rare cases, desmoid tumours can occur in pregnant women. This happens during pregnancy or after a surgical delivery. Many believe that this is caused by a combination of elevated hormones and surgery, however, the relationship between pregnancy and desmoid tumours is very rare and consists mostly of anecdotes in the scientific literature.
On ultrasonography, desmoid tumours appear as well-defined lesions with variable echogenicity. The lateral borders may appear ill-defined or irregular.
The CT appearance of desmoid tumours depends on their composition. They may appear homogeneous or heterogeneous and hypo-, iso-, or hyperintense compared with the attenuation of muscles. The degree of enhancement after the intravenous administration of contrast medium is variable [3, 4, 6].
Magnetic resonance imaging (MRI) features of desmoid tumours also show wide variability depending on the stage they are imaged. Characteristic MRI findings include poor margination, low signal intensity on T1-weighted images and heterogeneity on T2-weighted images, and variable contrast enhancement. Low T2 signal intensity bands are characteristic and represent foci of high concentrations of collagen deposition.
Definitive diagnosis must be established with histopathologic analysis.
The definitive treatment of desmoid tumours is wide local excision [5]. The recurrence rate of desmoid tumours is 20%– 30% depending on the location, extent, and completeness of the initial resection. The rate of recurrence is reduced if there is sufficient normal tissue surrounding the resected tumour [6]. Radiation therapy is used in patients with inoperable tumours, local recurrences, or incompletely excised lesions. Chemotherapy and endocrine therapy have also been used successfully to treat desmoid tumours [7, 8]
In conclusion, the history of painless abdominal mass, the age and sex of the patient, the location of the mass within the anterior abdominal wall, and the imaging features make desmoid tumour a strong primary diagnostic consideration. The radical resection with clear margins remains the principal determinant of outcome with the risk of local recurrence.

Differential Diagnosis List

Final Diagnosis

Desmoid tumour

URL:	https://www.eurorad.org/case/13526
DOI:	10.1594/EURORAD/CASE.13526
ISSN:	1563-4086