Endometrial carcinoma vs endometrial polyp: MR imaging findings

Clinical History

A 76-year-old woman was referred to the Gynaecology clinic for abnormal uterine bleeding. Endometrial biopsy revealed papillary serous endometrial adenocarcinoma of moderate differentiation. MR imaging of the pelvis followed.

Imaging Findings

MR imaging showed a heterogeneous mass, causing distension of the endometrial cavity (Fig. 1-3). The lesion was barely visible on T1-weighted images (Fig. 1c), heterogeneous on T2-weighted images, partly of intermediate signal intensity (Fig. 1b). The same component showed poor enhancement when compared to the normally enhancing myometrium (Fig. 2) and restricted diffusion (Fig. 3). Imaging findings were strongly suggestive of endometrial carcinoma. The junctional zone was intact. Neither cervical invasion, nor pelvic lymphadenopathy was revealed.
Part of the endometrial mass was also depicted heterogeneous, with an area of very low signal intensity on T2-weighted images and small, well-defined intratumoral cysts (Fig. 1b). This component showed strong, heterogeneous enhancement on late post-contrast T1-weighted images (Fig. 2). Imaging findings were suggestive of the coexistence of an endometrial polyp. The high ADC values of this part (Fig. 3) confirmed the diagnosis of benignity.
Histology following radical hysterectomy reported papillary serous endometrial adenocarcinoma (stage IA), coexisting with endometrial polyp.

Discussion

Background
Endometrial carcinoma represents the most common gynaecologic malignancy in many developed countries [1-3]. Most endometrial carcinomas are diagnosed at an early stage due to post-menopausal bleeding. Surgical treatment options depend on the local extent of the disease. MR imaging is recommended as the staging examination of choice in women with newly diagnosed endometrial carcinoma [1-3].
Endometrial polyps are common, with an incidence of 10-24%, usually seen at the age of 40-50 years and rarely after menopause [4-6]. They represent localized hyperplastic overgrowths of endometrial glands and stroma around a thick-walled vascular core, forming a sessile or pedunculated projection from the surface of the endometrium. Focal or diffuse dense fibrous tissue and sometimes smooth muscle are seen in the polyps. Cystic glandular hyperplasia often coexists [4]. Endometrial polyps are almost always benign. Less than 1% is associated with malignancy and the risk increases with advancing age [4-6].
Imaging Perspective
On MR imaging endometrial polyps are usually of intermediate signal intensity on T1-weighted images, with heterogeneous high signal intensity on T2-weighted images. Differentiation from endometrial carcinoma may be possible based on morphologic features. A central fibrous core, of low signal intensity on T2-weighted images and intralesional cysts that are small, smooth-walled sharply-defined hyperintense structures on T2-weighted images may strongly suggest the diagnosis of endometrial polyp. These findings were met in this case. After gadolinium administration, intense enhancement of the fibrous core may be seen [4-6]. However, biopsy in these patients is not obviated, partly due to the presence of microscopic carcinomas and the coexistence of polyps and carcinomas.
Endometrial carcinoma is usually detected with signal intensity similar to that of normal myometrium on T2-weighted images, enhancing less than myometrium on post-contrast T1-weighted images, as in this patient. Myometrial invasion and presence of necrosis proved of high predictive value for the diagnosis of malignancy [4].
Diffusion-weighted (DW) sequences are planned to identify alterations in thermally induced random (Brownian) motion of water molecules within tissues [7-11]. A variety of endometrial lesions were differentiated by Fujii et al based on DW imaging characteristics. Malignancies such as endometrial carcinoma and carcinosarcoma had lower ADC values than benign lesions including submucosal leiomyomas and endometrial polyps in this study [7]. In this patient, DW imaging characteristics increased the diagnostic confidence in differentiating between endometrial carcinoma and endometrial polyp. However, overlap between benign and malignant endometrial lesions may occur (e.g, celluar leiomyomas, necrotic or haemorrhagic tumours, low grade endometrial carcinomas).

Differential Diagnosis List

Final Diagnosis

Endometrial carcinoma coexisting with endometrial polyp.

URL:	https://www.eurorad.org/case/10442
DOI:	10.1594/EURORAD/CASE.10442
ISSN:	1563-4086