• Description of endometrial polyp types and MRI features. • Description of MRI features of endometrial carcinomas. • Review of endometrial polyps and endometrial carcinomas using case-based examples, highlighting distinctive clinical and imaging features.
Endometrial polyps and endometrial carcinomas are soft tissue lesions with different histopathologic features. At imaging, they usually present as polypoid lesions filling the endometrial cavity. Both clinical and radiological features of those lesions may overlap, however, there are some imaging pearls to distinguish them. Endometrial polyps are the most frequently endometrial pathologies in women with a peak incidence in the fifth decade. Polyps are usually benign lesions and typically asymptomatic (1). However, they may appear with abnormal uterine bleeding and infertility in some patients (2). Abnormal uterine bleeding is the most frequent symptom of the endometrial polyps and may occur in almost 68% of premenopausal and postmenopausal women (3). Endometrial carcinomas are the most frequently malignant tumor arising in the female reproductive system, occurring at an average age of 59 years. The clinical presentation is usually abnormal genital bleeding as endometrial polyps. As cytological examinations are limited in terms of sensitivity and specificity, endometrial curettage may be necessary based on imaging findings (4). Yet, endometrial carcinoma may occur on the background of a polyp, and it may be challenging to define the polyp and concurrent malignancy. The number of centers using frozen section diagnosis during routine hysterectomy is limited and not all institutions are able to make a decision of going on a further extensive surgery. Therefore, preoperative diagnosis with imaging features or curettage results is important to guide appropriate therapy options. In this poster, we aim to review the role of magnetic resonance imaging (MRI) in differentiating endometrial polyps from endometrial carcinomas, especially in patients who cannot undergo endometrial curettage or pipelle biopsy due to various reasons. ENDOMETRIAL POLYP Clinical features Endometrial polyps are abnormal growths of the inner lining of uterus (endometrium) which contain glands, stroma, and blood vessels. They are considered as neoplastic proliferations of the endometrial stroma with an admixed non-neoplastic glandular component. Hypertension, obesity, late menopause, and tamoxifen treatment are well known risk factors. Polyps can be multiple in 15%-26% of patients and may fill the entire cavity of the uterus (5). Polyps are often located in the fundus or uterine cornua which possess technical difficulties during curettage (6). Endometrial polyps can be pedunculated (with a narrow-elongated pedicle) or sessile (with a large flat base and no stalk) (7). They can range in size from 5 mm to as large as filling the entire uterine cavity. They are most frequently seen between the ages of 40 and 49 (8). Radiological features Transvaginal ultrasound and hysteroscopy have high sensitivity in the detection of polyps (89% and 96%, respectively). Nevertheless, MRI provides excellent contrast resolution for soft tissues and its multiplanar capability allows visualization of morphologic features as well as the extent of lesions, both of which are useful for deciding whether to perform abdominal/laparoscopic surgery or hysteroscopic resection. On MRI, endometrial polyps are characterized by a dense fibrous or smooth muscle stroma as well as glandular cystic dilatation that appears as "intratumoral cysts" on T2-weighted images (T2WI) (Figure1, Figure2). T2WI can differentiate most of the endometrial polyps from carcinoma based on their morphologic characteristics, such as "a central fibrous core" or "intratumoral cysts". "A central fibrous core" shows low signal intensity on T2-weighted sequences that is thought-provoking finding to differentiate from carcinomas with higher ADC values (Figure 3, Figure 4, Figure 5) (1,9-13). ENDOMETRIAL CARCINOMA Clinical features Endometrial carcinomas are the most frequent malignant tumor arising in the female reproductive system, occurring at an average age of 59 years. Endometrial carcinoma has been divided into two main categories as type 1 and type 2, from the clinical point of view. As cytological examinations are limited in terms of sensitivity and specificity, endometrial curettage may be necessary based on imaging findings (4). Recently, the potential importance of incorporating the molecular profile in the classification of endometrial cancer has been shown. Radiological features Endometrial cancers demonstrate lower ADC values than endometrial polyps (Figure 6) and are usually homogeneous with T2 intermediate signal intensity (14,15). Segmental thinning and/or distortion of the junctional area raises suspicion of myometrial invasion (4,16,17). The contrast-enhanced images clearly demonstrate the depth of invasion and the poor enhancement of the tumor compared to the myometrium (16,18). On dynamic MRI with gadolinium-based contrast agent, the inner muscle layer of the myometrium shows a rapid contrast enhancement than the outer muscle layer, and this enhancement pattern is similar in the postmenopausal endometrium (subendometrial enhancement). In postmenopausal patients with an unclear junctional zone, disruption of the subendothelial enhancement suggests myometrial invasion (19-21). For the differentiation of endometrial carcinoma from endometrial polyps filling the endometrial cavity, the most important feature is the demonstration of myometrial invasion. In addition, central fibrous core or intratumoral cysts are not expected findings for the carcinomas. However, radiologists should be aware of that T2 high signal necrotic areas may be seen in high grade endometrial carcinomas (Figure 7), and it is important to differentiate them from T2 hyperintense intratumoral cysts.
Figure 1. A 62-year-old woman with an endometrial lesion. Sagittal (A) and axial (B) T2W images shows well-defined polipoid mass in the endometrial cavity (yellow arrows) including intratumoral cysts which are clearly distinguishable within the polyp (blue arrows).
Figure 2. A 58-year-old woman with an endometrial lesion. Sagittal (A) and coronal (B) T2W images show well-defined, polipoid mass in the endometrial cavity is including intratumoral cysts (yellow arrows). The junctional zone is intact (green arrows).
Figure 3. A 60-year-old woman with an endometrial lesion. Coronal (A) and axial (B) T2W images show well-defined, polypoid mass in the endometrial cavity (yellow arrows) is including central fibrous septa (green arrows). The patient underwent a hysterectomy and histopathology confirmed an adenomyomatous polyp.
Figure 4. A 38-year-old woman with an endometrial lesion. Axial T2W (A) and ADC (B) images show well-defined, polipoid mass (yellow arrows) which has high ADC values.
Figure 5. A 49-year-old woman with an endometrial lesion. Coronal T2W (A) and post-contrast coronal T1W (B) images show small ‘’hard-to-see’’ polypoid mass (yellow arrow) and also an intramural uterine fibroma (asterisks). Post-contrast T1W image (B) shows intact subendometrial enhancement (blue arrows).
Figure 6. A 78-year-old woman with a uterine mass. Axial T2W (A) and ADC (B) images show well-defined, polipoid mass is including intratumoral cystic areas (yellow arrows). ADC image (B) shows very low values (red arrows) regarding malignancy in the right-sided solid component of the tumor. The patient underwent a hysterectomy and histopathology confirmed a carcinosarcoma.
Figure 7. A 62-year-old woman with a uterine mass. Sagittal (A) and axial (B) T2W images show ill-defined, polypoid mass in the endometrial cavity (yellow arrows) with an irregular necrotic area (asterisk). The junctional zone is disrupted. The patient underwent a hysterectomy and histopathology confirmed an endometrial carcinoma.
MRI is helpful in differentiating endometrial polyps from endometrial carcinomas. Radiologists should be aware of MRI features of those entities to guide the patients to the appropriate management especially when endometrial curettage or biopsy is not possible.