Pelvic deep aggressive angiomyxoma:Imaging finding in a rare case report

窦鑫 祁育芳

[Abstract]Deep aggressive angiomyxoma is an uncommon mesenchymal tumor， that is found predilection for the female pelvis at reproductive aye. We report CT appearances of a 42 year old woman with a deep aggressive angiomyxoma of the pelvis that was proven by preoperative biopsy. This article describes the imaging features of the tumor， which may help to know its characteristic of swirling or layering internal pattern. We further discuss disease characteristics， pathological characteristics， types， imaging features， differential diagnosis， treatment and prognosis.

[Key Words]：Tumor of the pelvis;  deep aggressive angiomyxoma;  CT;  MRI;  Pathology

【中圖分类号】R4  【文献标识码】A  【文章编号】1673-9026（2021）09-406-01

1.Introduction

Deep aggressive angiomyxoma is a rare， benign， mesenchymal tumor. It was first described by Steeper and Rosai in 1983. In 2013， WHO classified it as benign soft tissue tumor without well-defined differentiation. This tumor is called 'aggressive' due to frequent local recurrence rather than a propensity for distant metastatic disease [1]. Therefore， the main clinical features of this disease are high recurrence rate and strong invasion.

Most commonly presented in the female pelvis and perineum， but， there were also some cases occurring in the scrotum or spermatic cord in males[2]. The male to female ratio is 1：6[3]. This article reports a case of female pelvic deep aggressive angiomyxoma imaging features， and literature review， in order to deepen the understanding of this disease.

2.Case presentation

A 42-year-old woman， without a history of illness or drug use， presented to our radiology department with a large pelvic mass. No obvious inducement appeared in recent one month intermittent abdominal pain， accompanied by frequent urination， nearly 10 days conscious waist trapped.

After the hospital examination， the whole abdomen enhanced CT showed： irregular pelvic mass， about 19.6x8.3cm in size， with a CT value of about 18-30HU， and the lesion boundary was not clear. The enhanced scan showed progressive enhancement of solid parts， with a CT value of about 36HU in the arterial phase and 38HU in the venous phase and 7HU in the delayed phase. Finally， it was diagnosed as SBOT. Surgical findings： a soft， irregular mass， about 8X25x7cm in size in the pelvic and abdominal cavity， well demarcated from the surrounding organs， pedunculated， about 1.0cm in width， was located in the sigmoid colon—epiploic appendices. Pathological findings： a gray-yellow， gray-rad nodular mass， about 18x15x6cm in size， with a surface glossy smooth. The cut surface was grayish-yellow， some were gelatinous， and some areas were grayish-rad. Immunohistochemical： [ Corresponding author： Xin Dou. E-mail： 2223169080@qq.com]MDM2（-）， Ki-67（20%+）， CDK4（+）， S-100（-）， CD34（+）， CKpan（-）， Inhibin-a（-）， calretinin（-）， Desmin（+）， SMA（+）， CD163（+）， CD117（-）， DOG-1（-）， SOX-10（-）， Bcl-2（+）， STAT6（-）. Pathological diagnosis： according to the immunohistochemical results and clinical features， it was indicated that deep aggressive angiomyxoma （DAAM）.

3.Discussion

3.1 General characteristics

DAAM is a benign mesenchymal tumor that usually occurs in the pelvic cavity and perineum of a woman. It is common for premenopausal women. The peak age of DAAM is 30-40 years old[4]. It presents as a painless mass with local slow growth and is usually asymptomatic， the patient may touch or the huge tumor to the surrounding tissue organ compression， produces the local pain feeling， the lower abdomen is uncomfortable， the perineum drops pain and so on.

3.2 Pathological characteristics

The tumor volume is generally large， the largest one can reach 60 cm in the literature[5]. It is usually larger than 10 cm and has a soft mass with clear borders and a yellowish， gelatinous or fleshy cut surface. Microscopically， long rod-shaped or fusiform tumor cells are seen in the background of the mucinous stroma， interspersed with vessels of various sizes. Immunohistochemical： In Desmin， Vimentin， SMA， CD34， ER， PR is usually expressed in different degrees and S-100 is negative[6].

3.3 Types

There are two types of DAAM growth： pedunculated and infiltrative. Pedunculated growth is common in up to 1/3 of patients. The pedunculated is usually resection by local operation， the recurrence rate is low， but the initiative needs to expand the scope of operation， and local recurrence is easy[1].

3.4 Image characteristics

The CT appearance of DAAM was lower or equal density than that of muscle mass[7]. The inner density of DAAM was uneven. Plain CT scan showed low density area and cloud flocculent high density area. Irregular enhancement in arterial phase， gradual enhancement in venous phase and delayed phase， and sometimes typical spiral enhancement were seen. On MRI， the signal intensity on T1WI was almost equal to that on muscle， and the signal intensity on T2WI was high or mixed. Bands and swirls of low signal intensity were seen on T2WI. The low signal on T2-FS sequence showed more clearly， DWI showed limited diffusion of the mass， in contrast enhanced CT scan， there was obvious uneven enhancement with spiral or layered enhancement， which was the characteristic appearance of AAM reported in literature[8]. It may be related to the vascular maturity， the distribution and arrangement of the components of fibrous and vascular stroma[8]， and the high signal intensity of T2WI may be related to the water content and loose myxoid stroma of myxoma[9].

3.5 Identify with SBOT

SBOT is an adnexal tumor with low malignant potential. It is common in 15-70 years of age， and is more common in young patients. It is generally cystic and papillary in shape with a diameter of 2.5～10cm. The cut surface is bright and soft. A complex branching papillary structure with small papillary projections is seen here. CT or MRI scan showed solid and cystic mass， the cystic fluid showed water like density or signal， the wall and division showed papillary protuberance， DWI showed no obvious diffusion limitation， and the wall nodules showed obvious enhancement.

3.6 Treatment and prognosis

Because DAAM is invasive， large in size and deep in location， surgical resection is still the primary treatment. Because of its rich blood supply， preoperative vascular embolization can reduce the tumor blood supply[10]， reduce the tumor， thereby reducing the difficulty of surgery. For patients with positive PR and ER， Sereda etc[11] proposed GnRH-a treatment， which is helpful to reduce the size of tumors. In addition， tumor mitosis is rare， preoperative radiotherapy is ineffective[12]， but postoperative radiotherapy can inhibit tumor growth[13].

When the tumor invaded adjacent tissues or organs， it was difficult to resect completely. The recurrence rate was 33%-83%[14]， and there is generally no distant metastasis. Therefore， long-term follow-up and imaging examinations were needed to monitor the tumor recurrence.

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