Polypoid endometriosis: a mimic of malignancy

Abstract

This an interesting case of an asymptomatic 60-year-old postmenopausal patient with an incidental pelvic mass mimicking a pelvic malignancy on imaging. Biopsy revealed findings consistent with polypoid endometriosis. After discontinuation of hormone replacement therapy, the mass showed decrease in size on follow-up imaging. Polypoid endometriosis is a rare but distinct variant of endometriosis with histopathologic features akin to an endometrial polyp. Clinical and imaging features of polypoid endometriosis differ from classic endometriosis. While classic endometriosis predominates in premenopausal women, polypoid endometriosis more commonly affects peri- to postmenopausal women and is associated with the exposure to Tamoxifen or hormone replacement therapy. Imaging features that aid in the diagnosis of polypoid endometriosis are a T2 hyperintense polypoid mass with signal characteristics similar to endometrium, a T2 hypointense peripheral rim, contrast enhancement pattern mirroring the enhancement of the endometrium, and lack of diffusion restriction. Radiologists should be familiar with polypoid endometriosis because this clinically and morphologically distinct variant may mimic malignant neoplasms on imaging.

Keywords: Endometriosis-associated malignancy; Magnetic resonance imaging/MRI; Polypoid endometriosis.

Fig. 1

Axial T2-weighted image without fat saturation at the level of the cervix. A lobulated, heterogeneously T2-hyperintense mass (thick arrow) is shown to be centered in the cul-de-sac and inseparable from the cervical remnant (thin arrow) and anterior rectum (arrow head); the latter seems to be invaded by the mass

Fig. 2

Coronal T2 weighted images. Heterogeneously T2-hyperintense mass (thick arrow) with a T2-hypointense peripheral rim (thin short arrows)

Fig. 3

High b-value (b = 800 s/mm²) axial diffusion weighted image. The mass (arrow) is hyperintense on DWI

Fig. 4

Axial apparent diffusion coefficient (ADC) map. The mass (arrow) is relatively hyperintense with a mean value of 1.4 × 10⁻³ mm²/s (measurement not shown)

Fig. 5

Subtraction image from the axial post contrast 3D T1-weighted fat-suppressed image with fat saturation shows mild heterogeneous contrast enhancement of the mass (arrow)

Fig. 6

Photograph from flexible proctosigmoidoscopy taken at the level of the mid-rectum shows a round mass indenting the rectum (thick arrow) with relatively normal appearing mucosa

Fig. 7

Axial fused FDG-PET/CT image demonstrated mildly increased radiotracer uptake (arrow) in the mass with a maximal SUV of 3.3 (measurement not shown). Note the normal intense radiotracer activity in the partially imaged bladder which corresponds to the excreted radiotracer

Fig. 8

Hematoxylin and Eosin (H&E) image of the transvaginal biopsy specimen at 20× magnification shows a polypoid fragment of endometrial stroma (*) and glands (thin arrows) with thick-walled vessels (thick arrows), resembling an endometrial polyp

Fig. 9

(a) Hematoxylin and Eosin (H&E) image of the same biopsy specimen as above at 40× magnification shows simple tubular endometrial glands (thin arrows) lined by columnar cells embedded in stroma with ovoid spindle cells (*) resembling proliferative phase endometrium. (b) On CD10 immunohistochemistry, the stroma stains positive, confirming endometrial-type stroma, while the endometrial glands are negative. The unstained glands are irregularly dispersed with focal back-to-back crowding

Fig. 10

Axial T2-weighted images obtained (a) at initial presentation and (b) 3 months after the discontinuation of hormone replacement therapy showed a slight decrease in the size of the pelvic mass (arrow in a and b)