Post-ovarian cystectomy imaging appearances for borderline ovarian tumors: Pearls and pitfalls

Benjamin Jyhhan Kuo; Felicia Hui Xian Chin; Sung Hock Chew; Li Ching Lau

doi:10.25259/JCIS_197_2025

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Case Series

Genitourinary and Gynecologic Imaging

2026

:16;

doi:

10.25259/JCIS_197_2025

Post-ovarian cystectomy imaging appearances for borderline ovarian tumors: Pearls and pitfalls

Benjamin Jyhhan Kuo¹, Felicia Hui Xian Chin², Sung Hock Chew³, Li Ching Lau^1,

1Department of Diagnostic and Interventional Radiology, KK Women’s and Children’s Hospital, Singapore

2Department of Gynecological Oncology, KK Women’s and Children’s Hospital, Singapore

3Department of Pathology and Laboratory Medicine, KK Women’s and Children’s Hospital, Singapore.

*Corresponding author: Li Ching Lau, Department of Diagnostic and Interventional Radiology, KK Women’s and Children’s Hospital, Singapore. lau.li.ching@singhealth.com.sg

Received: 2025-08-06, Accepted: 2026-01-15, Published: 2026-04-10

Licence

This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial-Share Alike 4.0 License, which allows others to remix, transform, and build upon the work non-commercially, as long as the author is credited and the new creations are licensed under the identical terms.

How to cite this article: Kuo BJ, Chin F, Chew S, Lau L. Post-ovarian cystectomy imaging appearances for borderline ovarian tumors: Pearls and pitfalls. J Clin Imaging Sci. 2026;16:14. doi: 10.25259/JCIS_197_2025

Abstract

The Ovarian-Adnexal Reporting and Data System (O-RADS) ultrasound and MRI lexicon guidelines have standardized preoperative assessment of adnexal masses and improved communication with clinicians. However, in premenopausal women who have undergone ovarian cystectomy, post-operative ovarian appearances may mimic indeterminate or suspicious lesions, posing interpreting challenges. This illustrative educational case series highlights characteristic post-operative imaging features following cystectomy for borderline ovarian tumors (BOTs), emphasizing some common pearls and pitfalls. The cases underscore that while O-RADS is validated for preoperative adnexal assessment, post-operative ovaries constitute a recognized gray zone where familiarity with these imaging nuances is crucial for accurate interpretation.

Keywords

Borderline ovarian tumor

Cystectomy

Ovarian-adnexal reporting and data system

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INTRODUCTION

The Ovarian-Adnexal Reporting and Data System (O-RADS) ultrasound and MRI lexicon guidelines provide a validated and structured framework for the characterization of adnexal masses, improving consistency and communication to clinicians.^[1] The 2022 update offered further refinement in lesion descriptors and management recommendations.^[2,3] However, the post-operative ovaries represent a clinical gray-zone in which application of O-RADS should not be done in isolation as the residual ovarian stroma following cystectomy may mimic indeterminate and suspicious masses. This study focuses on post-ovarian cystectomy appearances in patients with borderline ovarian tumors (BOT), which comprise 15–20% of all epithelial ovarian neoplasms.^[4]

There is considerable imaging overlap between BOT and benign ovarian cystic lesions, limiting ultrasound diagnostic specificity in the pre-operative setting.^[5-7] BOTs are typically larger and may be associated with mildly raised ovarian serum biomarkers such as ovarian cancer-related tumor marker CA-125. Similarly, imaging overlap between BOT and low-grade invasive cancers is also well established with no reliable differentiating sonographic feature.^[6,8] BOTs are diagnosed at an earlier stage with more than 75% diagnosed at International Federation of Gynecology and Obstetrics (FIGO) stage 1 in contrast to ovarian cancer (25% at FIGO stage 1).^[9] While the prognosis of BOTs is excellent with a reported 5-year survival rate for FIGO stage 1 disease of 95–97%, there remain certain relatively more aggressive subtypes with a propensity for recurrence giving a total 10-year survival rate of 70–95%.^[10] Furthermore, patients with BOTs are typically more than 10 years younger than those diagnosed with epithelial ovarian cancer with many patients being candidates for fertility-sparing surgery.^[11]

Given the epidemiological characteristics of BOT and prognostic outcome, conservative management has become more feasible. Available data from literature have indicated the recurrence rate for BOTs following conservative surgery with cystectomy to be 10–30% compared with 5% following radical surgery.^[12] Given these trends, accurate imaging follow-up after fertility-sparing surgery with ovarian cystectomy is particularly pertinent. The imaging appearances of the post-operative ovary following cystectomy are variable and are related to surgical changes, the size of the pre-operative ovarian lesion, and presence of residual or recurrent disease.^[13]

While it is desirable to intervene early to diagnose recurrence or malignant transformation, balancing aggressive follow-up in this context with the need to minimize unnecessary imaging can be challenging. Furthermore, this balancing act becomes all the more difficult given that the post cystectomy ovary imaging appearances are often variable and may resemble that of a suspicious or indeterminate mass. To our knowledge, there has been limited literature on the topic. Through this illustrative case series, we offer an approach and share pearls and pitfalls along with features of benignity when interpreting post-ovarian cystectomy studies [Table 1].

Table 1: Case series of large borderline ovarian tumors following ovarian cystectomy in premenopausal women. Follow-up imaging characteristics demonstrate features of a chronically stretched ovarian stroma manifested as a tubular structure of alternating bands of echogenicity stacked on each other. Application of O-RADS (Ovarian-Adnexal Reporting and Data System) in these clinical contexts should be performed knowing these imaging nuances.

Case	Patient age (years)	Size of ovarian lesion (cm)	Pre-operative O-RADS	Histopathology	Post-operative imaging feature	Outcome
Case 1	20	24.8	3	Borderline mucinous tumor	Crenulated outer margin folding and collapsing on itself.	Stable on follow-up.
Case 2	21	21.3	3	Borderline mucinous tumor	Stretched ovary with an elongated tubular morphology without significant vascularity.	Stable on follow-up.
Case 3	22	23.0	3	Borderline mucinous tumor	Tubular structure in the left adnexa folding and collapsing on itself without solid enhancing component.	Negative for recurrence on subsequent left salpingo-oophrectomy. Eventual diagnosis of peritoneal tuberculosis.

METHODS

This retrospective educational case series was conducted at a tertiary referral center between January 01 and June 30, 2024. Cases were identified through institutional picture archiving and pathology databases. Inclusion criteria were:

Premenopausal women with histologically confirmed BOTs
Prior ovarian cystectomy with ovarian preservation
Availability of post-operative ultrasound and/or MRI imaging within 24 months after surgery.

Clinical and imaging follow-up were reviewed where available to confirm stability and benign evolution. The study complied with institutional research guidelines for retrospective studies.

Ethical considerations

Institutional review board approval was waived for this retrospective educational case series involving anonymized images. Written informed consent for publication was obtained, and the study was conducted in accordance with the Declaration of Helsinki.

CASE SERIES

Case 1

The first case was a 20-year-old woman with chronic dyspepsia of 6-month duration not improving with conservative management. Her initial abdominal ultrasound study demonstrated an O-RADS 3 midline multiseptated cystic mass measuring up to 24.5 cm, arising from the left ovary with compressive mild-to-moderate right hydroureteronephrosis [Figure 1a and b]. On CT, the mass shows thickened and enhancing internal septation [Figure 1c]. The patient underwent ovarian cystectomy, omentectomy with peritoneal washing which eventually confirmed a borderline mucinous tumor. The omentectomy and peritoneal washing were negative for malignancy.

A 20-year-old woman with chronic dyspepsia. (a) Pelvic ultrasound transabdominal approach grayscale longitudinal orientation pre-operative evaluation demonstrates a multilocular cyst measuring up to 24.5 cm, classified as O-RADS 3, arising from the right ovary. (b) Color Doppler transverse orientation shows no internal vascularity. (c) Contrast-enhanced CT coronal plane demonstrates areas of thickened septations within the predominantly cystic mass (yellow arrow).

The patient’s 3-month post-operative follow-up ultrasound revealed a solid slightly tubular structure in the right adnexa with scattered vascularity and cystic spaces. It was classified as US O-RADS 4 [Figure 2a and b]. On MRI pelvis, the solid component of the adnexal mass was noted to be T1W isointense, T2W hypointense without corresponding enhancement, or restricted diffusion [Figure 2c and d]. It has a crenulated outer margin seen folding and collapsing on itself. Further serial ultrasound follow-up studies (not shown) demonstrated stability in morphology and size.

A 20-year-old woman with chronic dyspepsia. (a) Pelvic ultrasound transvaginal approach, grayscale coronal orientation following right ovarian cystectomy for borderline mucinous tumor demonstrates a solid convoluted structure (yellow arrow). (b) Color Doppler coronal plane shows scattered vascularity in the right adnexa, featuring a thick T2 hypoechoic outer layer (blue arrow) and tiny cystic spaces. This finding was classified as O-RADS 4. (c) Coronal T2-weighted non-fat-suppressed magnetic resonance (MR) demonstrates a thick T2 hypointense outer layer (yellow arrow), while the center is T2 hyperintense. (d) Coronal T1-weighted fat-suppressed gadolinium-enhanced MR shows no post-contrast enhancement (blue arrow).

Case 2

The second case was a 21-year-old woman who presented with a 2–3-month history of pelvic and abdominal fullness. The transabdominal pelvic ultrasound study demonstrated a large 21.3 cm cystic mass with internal echoes and thin septations. It is seen superior to the uterus and urinary bladder, extending to the upper abdomen [Figure 3a and b]. No intrinsic solid component was evident. No solid component or mural irregularity was identified on MRI pelvis [Figure 3c and d]. A left ovarian cystectomy was performed and the mass was proven to be a borderline mucinous tumor. The 6-month post-operative follow-up ultrasound study demonstrated a 6.1cm elongated heterogeneous hypoechoic mass in the left adnexa with no discernible vascularity or definite follicles within [Figure 4a and b]. Further characterization with MRI demonstrated the structure to be predominantly T1W isointense and T2W heterogeneous iso-hypointense without enhancement or restricted diffusion [Figure 4c and d].

A 21-year-old female with pelvic fullness. (a) Pelvic ultrasound transabdominal approach grayscale longitudinal orientation pre-operative evaluation demonstrates a large cystic mass with internal echoes and thin septations measuring up to 21.3 cm (yellow arrow) superior to the uterus and urinary bladder. (b) Color Doppler transverse orientation shows no discernible intrinsic solid component (yellow arrow). (c and d) Coronal and sagittal T2-weighted non-fat-suppressed magnetic resonance images demonstrate smooth inner walls, incomplete septations, and no mural irregularity. The impression was a benign ovarian epithelial neoplasm, possibly a serous cystadenoma.

A 21-year-old woman following ovarian cystectomy for a borderline mucinous tumor. (a) Pelvic ultrasound transabdominal approach grayscale longitudinal orientation reveals an elongated heterogeneous hypoechoic structure measuring up to 6.1cm (yellow arrow), located posterior to the uterus on the right. (b) Color Doppler transverse orientation shows no discernible vascularity or definite follicles observed within. (c) Axial T2-weighted non-fat suppressed magnetic resonance (MR) shows the ovary to exhibit a convoluted appearance, featuring a thick T2 hypointense outer layer (yellow arrow) and a T2 hyperintense center. (d) Axial T1-weighted fat-suppressed gadolinium-enhanced MR shows no post-contrast enhancement (blue arrow) or significant restricted diffusion (not shown). A few follicles were observed within.

Case 3

The third case was a 22-year-old woman who was referred for a pelvic mass. The initial screening pelvic ultrasound study was not available. CT demonstrated a large 23cm unilocular cystic lesion likely of left ovarian in origin with resultant compressive bilateral hydronephrosis without overt distant metastasis or adenopathy [Figure 5a and b]. The patient underwent left ovarian cystectomy which confirmed a borderline mucinous tumor.

A 22-year-old female with chroni pelvic fullness.(a) Coronal contrast-enhanced CT pre-operative evaluation demonstrates a large 23 cm unilocular cyst (yellow arrow), likely of left ovarian origin. (b) Sagittal contrast-enhanced CT. There is no evidence of overt distant metastasis or lymphadenopathy.

The post-operative follow-up ultrasound demonstrated a tubular hypoechoic structure in the left adnexa with scattered vascularity [Figure 6a and b]. This remained stable for 1-year post-surgery. An MRI pelvis was performed later in view of rising ovarian cancer-related tumor marker CA-125. The MRI showed a tubular structure in the left adnexa folding and collapsing on itself without solid enhancing component [Figure 6c]. However, there was diffuse peritoneal thickening, enhancement, and restricted diffusion [Figure 6d-f] which at the time was concerning for disease progression. The staging CT study did not demonstrate distant metastasis in the thorax aside from foci of centrilobular nodularity and bronchial dilatation in the apices of the lung, most prominent on the right, likely due to small airway inflammatory/ infective changes and peritoneal thickening in the pelvis [Figure 7a and b].

A 22-year-old woman 6 months following left ovarian cystectomy for a borderline mucinous tumor. (a) Pelvic ultrasound transvaginal approach grayscale sagittal orientation demonstrates a convoluted hypoechoic structure in the left adnexa with hypoechoic outer layer (yellow arrow). (b) Color Doppler sagittal plane shows scattered vascularity. (c) Coronal T2-weighted non-fat suppressed magnetic resonance (MR) evaluation with rising ovarian cancer-related tumor marker CA-125 shows the convoluted structure seen on the postoperative ultrasound displays a thick T2 hypointense outer layer (yellow arrow) containing a few follicles and a T2 hyperintense center. The right ovary is normal in appearance. (d) Axial T2-weighted non-fat-suppressed MR shows new small-volume ascites and diffuse peritoneal thickening (blue arrow). (e and f) Diffusion-weighted imaging (DWI) and apparent diffusion coefficient (ADC) MRI images demonstrate associated restricted diffusion (red arrow). The concern at the time was metastatic disease.

A 22-year-old woman following left ovarian cystectomy for a borderline mucinous tumor, followed by rising ovarian cancer-related tumor marker CA-125 and diffuse peritoneal thickening and enhancement on pelvic MRI. (a) Axial contrast-enhanced CT of the pelvis demonstrates ascites (red asterisk) and enhancement of the thickened peritoneum (yellow arrow). (b) Coronal CT of the thorax in lung window shows centrilobular nodularity and bronchial dilatation in the apices of both lungs (blue arrow).

Following a multidisciplinary tumor board discussion, the patient underwent diagnostic laparoscopy, left salpingooophrectomy, and peritoneal and omental biopsy. The surgical findings revealed extensive miliary peritoneal disease covering the peritoneum, the uterus, the right ovary, and the enlarged left ovary. The left ovary showed a corrugated surface [Figure 8a-d]. The histology eventually confirmed florid granulomatous inflammation diffusely along the peritoneal surface and coating the pelvic organ structures [Figure 8e-g]. The enlarged left ovary itself showed a thick collagenous wall, without lining cells and focal areas of ovarian-type stroma. No malignant cells were seen within the left ovary. The rest of the omentum and peritoneum showed acid-fast bacilli with no evidence of malignancy. The patient went on to receive therapy for tuberculosis and demonstrated significant clinical and radiological improvement following treatment.

Laparoscopic images during a second surgery of a 22-year old woman on clinical suspicion for invasive disease progression for a left ovarian borderline mucinous tumor with diffuse peritoneal thickening and enhancement. (a-d) Laparoscopic intraoperative images of the peritoneum, uterus, right and left ovaries reveal extensive miliary disease. As seen on prior magnetic resonance (MR), the left ovary is significantly larger than the right and has a crenulated surface. (e) Histopathological slides hematoxylin and eosin (H&E, magnification x 20) of the left ovary demonstrates aggregate of closely-packed granulomas composed of epithelioid macrophages with occasional multinucleated giant cells coating the serosa (red arrow). The ovarian parenchyma is hypocellular with increased fibrosis with no features of malignancy (blue arrow). (f) Histopathological slides H&E, magnification x 20, of the fallopian tube reveals aggregates of epithelioid granulomas within tubal mucosa (blue arrow) and in the paratubal tissue (red arrow). (g) Histopathological slides H&E, magnification x 20, of the omentum reveals aggregates of granulomas (blue arrow).

DISCUSSION

Teaching point 1: Application of O-RADS in the context of the post-operative ovary should not be interpreted in isolation

The indications for ovarian cystectomy are often a combination of patient symptoms or an O-RADS 3 category lesion, often times a BOT.^[14] While the O-RADS guidelines are intended to risk-stratify ovarian or adnexal abnormalities, there has been limited literature on its application in the post-operative ovary. One study from 2004 reported a 10% recurrence rate of ovarian endometrioma following cystectomy within a 6-month follow-up period.^[13] However, there was limited information on the sonographic features of the post-operative ovary and whether the surgical changes may mimic indeterminate masses. There is even further limited information in the literature on sonographic follow-up for BOT in premenopausal women.^[5,15] The ovarian post-cystectomy collapsed shell often meets criteria for O-RADS 4 or 5 based on solid-appearing components. Applying US O-RADS to post-cystectomy ovaries may overestimate malignancy risk and lead to unnecessary further imaging and re-operation. Radiologists should therefore interpret such findings descriptively, correlating with surgical history and stability on follow-up.

Teaching point 2: Recognize the “Collapsed Shell” morphology

In the presence of a large ovarian cyst, the ovarian capsule and its stroma around the cyst are chronically stretched and undergo fibrosis. Following cystectomy, the fibrosed capsule and stroma would not involute to normal size. Instead, they fold and collapse inward creating a tubular or ovoid structure with alternating echo-texture on ultrasound where the hypoechoic bands represent the fibrosed capsule and stroma while the more echogenic bands represent the non-fibrosed stroma. Follicles may be identified in the fibrosed stroma. However, identifying follicles can be challenging through a transabdominal scan which was usually performed for younger, sexually inactive patients. MRI more clearly depicts the fibrosed capsule as T1 and T2 hypointense, while the non-fibrosed stroma and post-cystectomy cystic space appear hyperintense on T2-weighted images. Follicles, if present, are easily identifiable on MRI [Table 2].

Table 2: Sonographic and MRI features of the “collapsed shell” representing benign features following ovarian cystectomy for large borderline ovarian tumors.

Imaging element: benign collapsed shell	Benign ultrasound features	Benign MRI features
Morphology	Tubular or ovoid structure	Tubular or ovoid structure
Internal contents	Alternative hypoechoic and echogenic bands	T1 and T2 hypointense fibrosed capsule
Ancillary features	Minimal preserved vascularity	T2 hyperintense non-fibrosed or residual cystic component Residual follicles if present

This case series is limited by its small sample size and single-institution scope, focusing on illustrative examples. No interobserver variability or diagnostic accuracy assessment was performed. The findings are descriptive and educational, intended to highlight imaging morphological patterns rather than to propose new diagnostic criteria or modify O-RADS recommendations.

CONCLUSION

Post-cystectomy ovarian morphology can mimic suspicious adnexal lesions if interpreted using pre-operative O-RADS criteria in isolation. Recognizing the “collapsed shell” appearance characterized as an elongated or tubular structure with alternating hypoechoic bands and preserved vascularity helps avoid false-positive interpretation. MRI aids confirmation, demonstrating hypointense fibrosed stroma without enhancement or diffusion restriction.

It is also important for radiologists to be aware that this sign is not specific to post-BOTs cystectomy but can also be seen in other cases where large cysts or endometriomas had been removed. Awareness of this appearance enables radiologists to confidently identify benign post-operative changes, reduce unnecessary examinations, and alleviate patient anxiety.

Ethical approval:

Institutional Review Board approval was waived for this retrospective educational case series.

Declaration of patient consent:

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patients have given their consent for their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Conflicts of interest:

There are no conflicts of interest.

Use of artificial intelligence (AI)-assisted technology for manuscript preparation:

The authors confirm that there was no use of artificial intelligence (AI)-assisted technology for assisting in the writing or editing of the manuscript and no images were manipulated using AI.

Financial support and sponsorship: Nil.

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