Aggressive angiomyxoma of the pelvis

Clinical History

A gravid 28-year-old G2P1 in her third trimester presents with a 3-year history of an increasing painless vaginal mass that prolapses from her vagina. The mass is present on straining and reduces spontaneously. No significant past medical history is otherwise noted.

Imaging Findings

Pelvic MRI with injection of gadolinium contrast was performed. A large mass is located in the pelvic cul-de-sac that displaces the uterus, vagina and bladder anteriorly and the rectum and sigmoid posteriorly. The mass is 12 x 11 x 20 cm and is elongated cranio-caudally, limited by the pelvic sidewalls. The mass extends superiorly to the level of the L4-L5 disc and inferiorly in the deep cul-de-sac at the level of anal canal. It is well-defined and there are no signs of local invasion.

On T2-weighed images, it has a swirled pattern and has heterogeneous areas of hyperintensity traversing craniocaudally (Figure 1 and 2). On T1-weighted images, it is homogenously isointense (Figure 3). There are heterogeneous linear areas of enhancement seen on post gadolinium T1-weighted images, giving an onion-peel appearance (Figure 4).

Discussion

Aggressive angiomyxoma (AA) is a rare myxoid mesenchymal neoplasm that occurs frequently in the pelvic and perineal regions [1]. The tumour often presents as a solitary lesion, has a female to male ratio of 6:1, and is frequently found in women of reproductive age group [2]. It is a locally invasive tumour with a high rate of recurrence, but it typically does not metastasize. AA is a slow-growing tumour and ranges between 10 and 20 cm [2, 3].

AA commonly presents as fullness of pelvic region, abdominal distension, urinary frequency and constipation. Rapid growth of the tumour has been observed during pregnancy because of the presence of oestrogen and progesterone receptors [4].

MR imaging demonstrates hyperintense lesion on T2-weighted images with a heterogeneous swirled pattern due to the high composition of myxoid elements (Figures 1 and 2). On T1-weighted images, the mass is isointense (Figure 3), while post-gadolinium T1-weighted images shows linear areas of enhancement (Figure 4). Due to the large size of these tumours, it often has mass effect on the surrounding structures including the uterus, bladder and ovaries [3]. On imaging, it is important to recognize if there is extension beyond the pelvic diaphragm into the perineal area. This helps the surgeon in planning wide margin resection during surgery.

The definitive treatment for AA is surgery with wide local excision [5]. Complete excision is difficult to achieve due to the locally invasive nature of the disease, though pre-operative MRI is helpful as it defines the extent of the tumour. Adjuvant treatments, including hormonal therapy and GnRH agonists have been used in cases where surgical treatment carries high morbidity and mortality risk [5, 6].

Differential Diagnosis List

Final Diagnosis

Aggressive angiomyxoma of the pelvis

URL:	https://www.eurorad.org/case/12298
DOI:	10.1594/EURORAD/CASE.12298
ISSN:	1563-4086