Polypoid endometriosis mimicking aggressive pelvic malignancy on MRI in a premenopausal woman: A case report

A 40-year-old woman presented to her primary care physician with abnormal uterine bleeding, reporting the use of approximately three sanitary pads on heavy days and one pad on lighter days. She denied associated uterine cramping, pelvic pain, or other systemic symptoms. A Papanicolaou smear was performed, during which a mass protruding from the uterus was noted. She was subsequently referred to an obstetrics and gynecology clinic, where pelvic examination raised suspicion for a uterine fibroid. Oral contraceptive pills were initiated for medical management of her bleeding; however, this resulted in only minimal symptomatic improvement. Due to a persistent concern for a uterine mass, she was referred to gynecologic oncology for pelvic MRI and further evaluation. Pelvic MRI demonstrated a lobulated polypoid mass along the posterior aspect of the lower uterus and cervix ( Fig. 1 ). On T2-weighted images, the lesion was predominantly hyperintense with a thin peripheral T2-hypointense rim and spiculated low-signal-intensity strands extending posteriorly into adjacent tissues. Ill-defined T2-hypointense foci within the posterior uterine wall were also noted, compatible with adenomyosis. Although these findings were suggestive of endometriosis-related pathology, the spiculated margins, apparent infiltrative extension, and associated mass effect imparted an aggressive appearance, raising concern for possible malignant infiltration. Fig. 1 (A) Non-contrast axial T2-weighted and (B) axial T1-weighted images demonstrate an oval right adnexal lesion that is relatively hypointense on T2-weighted imaging and hyperintense on T1-weighted imaging (white arrows), consistent with an endometrioma. Internal dependent T2-hyperintense areas (red arrow) likely represent blood products or clot. (C) Coronal and (F) sagittal T2-weighted images demonstrate a lobulated polypoid hyperintense mass along the posterior aspect of the lower uterus (white arrows). Ill-defined T2-hypointense foci within the posterior uterine wall are compatible with adenomyosis. (D) Axial T2-weighted and (E) axial T1-weighted images show the same polypoid lesion, which is hyperintense on T2-weighted imaging and isointense on T1-weighted imaging, with a thin peripheral T2-hypointense rim (white arrows) and posterior spiculated T2-hypointense strands (red arrows), imparting an aggressive, mass-like appearance. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.) Fig. 1 (A) Non-contrast axial T2-weighted and (B) axial T1-weighted images demonstrate an oval right adnexal lesion that is relatively hypointense on T2-weighted imaging and hyperintense on T1-weighted imaging (white arrows), consistent with an endometrioma. Internal dependent T2-hyperintense areas (red arrow) likely represent blood products or clot. (C) Coronal and (F) sagittal T2-weighted images demonstrate a lobulated polypoid hyperintense mass along the posterior aspect of the lower uterus (white arrows). Ill-defined T2-hypointense foci within the posterior uterine wall are compatible with adenomyosis. (D) Axial T2-weighted and (E) axial T1-weighted images show the same polypoid lesion, which is hyperintense on T2-weighted imaging and isointense on T1-weighted imaging, with a thin peripheral T2-hypointense rim (white arrows) and posterior spiculated T2-hypointense strands (red arrows), imparting an aggressive, mass-like appearance. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.) Post-contrast fat-suppressed T1-weighted images ( Fig. 2 ) demonstrated heterogeneous enhancement of the polypoid mass, further heightening suspicion for malignancy. A right adnexal oval lesion demonstrated intrinsic T1 hyperintensity, relative T2 hypointensity, and lack of post-contrast enhancement, consistent with an endometrioma containing dependent blood products; however, the right ovary was not separately identified. Fig. 2 Post-contrast T1 weighted fat sat axial (A, B), coronal (C), and sagittal (D) images show heterogenous enhancement of the polypoid mass along the posterior aspect of the uterus (white arrows). Right adnexal non-enhancing oval structure (red arrow) consistent with endometrial cyst. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.) Fig. 2 Post-contrast T1 weighted fat sat axial (A, B), coronal (C), and sagittal (D) images show heterogenous enhancement of the polypoid mass along the posterior aspect of the uterus (white arrows). Right adnexal non-enhancing oval structure (red arrow) consistent with endometrial cyst. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.) Given the complex imaging features and concern for possible malignant transformation, the patient underwent a total abdominal hysterectomy, bilateral salpingectomy, right oophorectomy, resection of the complex pelvic mass, and upper vaginectomy. Gross and histopathologic examinations revealed multiple red-brown nodular to polypoid masses arising from the cervical mucosa, consistent with endometriosis ( Fig. 3 ). Additionally, extensive endometriosis was identified involving the right ovary, uterine sidewall, and an umbilical hernia, along with extensive adenomyosis of the uterus ( Fig. 4 ). No evidence of malignancy was identified. Fig. 3 Cervical mucosa with multiple red-brown nodular to polypoid masses projecting from the surface. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.) Fig. 3 Fig. 4 H&E-stained slide from a nodular cervical mass showing endometrial-type stroma with cystically dilated endometrial glands (left) beneath overlying cervical squamous epithelium (right), consistent with endometriosis involving the cervix (40×). Fig. 4 Cervical mucosa with multiple red-brown nodular to polypoid masses projecting from the surface. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.) H&E-stained slide from a nodular cervical mass showing endometrial-type stroma with cystically dilated endometrial glands (left) beneath overlying cervical squamous epithelium (right), consistent with endometriosis involving the cervix (40×). The patient had an uncomplicated postoperative course and was discharged on postoperative day 3, with regular follow-up by gynecologic oncology; at one year there had been no recurrence of abnormal uterine bleeding or other related symptoms.

This work did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors .

Written consent was obtained from the patient for publication of the case report and accompanying images.

Polypoid endometriosis is a rare but important benign entity that can closely mimic aggressive pelvic malignancy on MRI. Although traditionally associated with peri- or postmenopausal status and estrogen exposure, recent literature demonstrates that it can occur in younger, premenopausal, and even pregnant patients without identifiable risk factors. Its mass-forming appearance, heterogeneous signal characteristics, avid enhancement, and apparent infiltrative behavior represent a significant diagnostic pitfall. Awareness of this entity, careful evaluation of MRI features, and integration of clinical context are essential for accurate preoperative assessment. Inclusion of polypoid endometriosis in the differential diagnosis of aggressive-appearing pelvic masses may help prevent unnecessary extensive oncologic surgery and histopathologic confirmation remains critical for definitive diagnosis.

Polypoid endometriosis is an uncommon but clinically important variant of endometriosis that poses a significant diagnostic challenge due to its striking resemblance to malignant pelvic tumors [2] , [3] . Histologically, it consists of benign endometrial glands embedded within CD10-positive endometrial-type stroma, often forming large polypoid or multinodular masses without cytologic atypia or destructive stromal invasion [2] , [3] . Despite its benign nature, its gross appearance and imaging characteristics frequently lead to misdiagnosis as an aggressive neoplasm. Epidemiologically, polypoid endometriosis differs from classic endometriosis. While conventional endometriosis is primarily a disease of reproductive-age women, it has been reported more commonly in peri- and postmenopausal patients [2] , [3] . Many cases have been associated with exogenous estrogen exposure, including hormone replacement therapy and tamoxifen use, supporting hormonally driven pathogenesis [4] , [5] , [12] . Tamoxifen, a selective estrogen receptor modulator, has estrogenic effects on endometrial tissue and has been repeatedly implicated in the development of polypoid endometriosis [5] . More recent literature, however, challenges this traditional paradigm. Several case reports and small series describe polypoid endometriosis in adolescents, young premenopausal women, and during pregnancy, even in the absence of hormonal therapy or prior gynecologic surgery [6] , [7] , [8] . These findings suggest that additional, yet poorly understood, mechanisms may contribute to its pathogenesis and emphasize that reliance on age or hormonal history alone may be misleading. MRI is the imaging modality of choice for characterization of these lesions. Typical MRI features include lobulated or polypoid masses demonstrating intermediate to high signal intensity on T2-weighted images, often with internal heterogeneity reflecting glandular and stromal components [9] , [10] , [11] . Areas of T1 hyperintensity may be present due to hemorrhagic foci, although these are not universally observed [9] . Following contrast administration, lesions frequently show avid or heterogeneous enhancement that may closely mimic malignant tumors [10] . A peripheral low-signal-intensity rim on T2-weighted images, thought to represent fibrous tissue or compressed surrounding structures, has been described as a potentially helpful diagnostic clue [9] . Diffusion-weighted imaging findings are variable. While many cases demonstrate no true diffusion restriction, some lesions may appear to be hyperintense on high b-value images, further mimicking malignancy and complicating interpretation [10] . Additionally, polypoid endometriosis may exhibit mass effect or apparent infiltration of adjacent organs such as the rectosigmoid colon, bladder, vaginal stump, or pelvic peritoneum, closely simulating advanced pelvic cancer or peritoneal carcinomatosis [6] , [9] . Mild FDG uptake has also been reported on PET/CT, limiting the specificity of functional imaging in this context [11] . The differential diagnosis for aggressive-appearing pelvic masses on MRI includes ovarian carcinoma, endometrial carcinoma, uterine sarcoma, gastrointestinal stromal tumors, and endometriosis-associated malignancy [6] . Correlation with clinical history, prior endometriosis, and estrogen exposure is helpful; however, histopathologic confirmation remains the gold standard for diagnosis, demonstrating benign endometrial glands and stroma without malignant cytologic features [2] , [3] . Recognition of polypoid endometriosis is crucial to avoid overtreatment. Increased familiarity with its expanding demographic range, clinical associations, and MRI features can help radiologists suggest this diagnosis prospectively and potentially prevent unnecessary radical surgical intervention [6] , [9] .

This article was not commissioned and was peer reviewed.

Arun Arumugam contributed to conception of the case report, drafting the manuscript, undertaking the literature review and revising the article critically for important intellectual content. Trisha Patil contributed to conception of the case report, drafting the manuscript, undertaking the literature review and revising the article critically for important intellectual content. Brandol Wolfenbarger contributed to patient care, acquiring and interpreting the data, drafting the manuscript and revising the article critically for important intellectual content. Luis Velasquez-Zarate contributed to patient care, acquiring and interpreting the data, drafting the manuscript and revising the article critically for important intellectual content. Abdul-Rahman AbuAlruz contributed to patient care, conception of the case report, acquiring and interpreting the data, drafting the manuscript and revising the article critically for important intellectual content. Ravishankar Pillenahalli Maheshwarappa contributed to patient care, conception of the case report, drafting the manuscript, acquiring and interpreting the data, and revising the article critically for important intellectual content. All authors approved the final submitted manuscript.

Endometriosis is a benign gynecologic condition defined by the presence of endometrial glands and stroma outside the uterine cavity and affects approximately 10–15% of women of reproductive age [1] . Polypoid endometriosis is a rare and distinct variant characterized by florid, polypoid, mass-forming endometrial tissue that can closely resemble malignant neoplasms both clinically and radiologically [2] . This entity was first described by Mostoufizadeh and Scully in 1980 and later further characterized in small clinicopathologic series [3] . Unlike typical endometriosis, which predominantly affects premenopausal women, polypoid endometriosis has historically been reported more frequently in peri- and postmenopausal patients [2] , [3] . A strong association has been described with estrogenic stimulation, including hormone replacement therapy and tamoxifen use [4] , [5] . However, recent reports have broadened the recognized demographic spectrum, documenting cases in younger premenopausal women, adolescents, and during pregnancy, even in the absence of exogenous hormonal exposure [6] , [7] , [8] . Clinically, polypoid endometriosis often presents as a large pelvic or abdominal mass and may involve the ovary, rectosigmoid colon, bladder, vaginal cuff, or peritoneum, frequently raising concern for gynecologic or gastrointestinal malignancy [2] , [6] , [9] . On magnetic resonance imaging (MRI), these lesions may demonstrate apparently aggressive features such as heterogeneous T2 signal intensity, avid enhancement, mass effect, and apparent invasion of adjacent structures [9] , [10] , [11] . Diffusion-weighted imaging findings may further complicate differentiation from malignant tumors [10] . Due to its rarity and overlapping imaging characteristics, preoperative diagnosis remains challenging, and misinterpretation may result in unnecessary extensive oncologic surgery [6] , [9] . Awareness of this rare entity and its MRI features is therefore critical for accurate diagnosis and appropriate management.

The authors declare that they have no competing interest regarding the publication of this case report.