Extraovarian Brenner tumor in the uterus: a case report and review of literature

Abstract

Background: Extraovarian Brenner tumors (EOBTs) are extremely rare and can be observed incidentally in both female and male patients, raising concerns regarding the origin of Brenner tumors.

Case presentation: A 53-year-old postmenopausal woman presented with a nodular lesion in the left side of the corpus uteri, which was found at a routine health check. Macroscopically, the lesion appeared as a solid nodule with a yellowish-gray cut surface, approximately 6 cm in greatest diameter. Microscopically, the lesion consisted of well-defined epithelial nests and spindled stromal cells. Parenchymal cells expressed CK7, GATA3, CK5/6, 34βE12, and p63. A single layer of cavity-lined cells with umbrella-like shape showed apical Uroplakin III positivity. Stromal cells were positive for SMA, ER, and PR. The final diagnosis was EOBT and the patient was followed for 2 months with no recurrence.

Conclusions: We report here the third case of EOBTs in the uterus. The combination of morphologic and immunohistochemical results supported the involvement of urothelial metaplasia in the development of EOBTs. The similarities between EOBTs and Walthard nests made Müllerian epithelium an attractive candidate as the cellular origin. Changes of tissue structure or sex hormones imbalance may lead to the translocation of Müllerian remnants to distant organs, explaining the pathogenesis of EOBTs.

Keywords: Brenner tumor; Extraovarian; Pathogenesis; Uterus; Walthard nest.

Fig. 1

The sonographic findings of the uterine EOBTs. A hypoechoic mass measured 5.2 x 5 x 4.7 cm was detected incidentally 2 years ago (a). The lesion was indolent, approximately 5.8 cm in greatest diameter (b)

Fig. 2

Histopathological features of EOBTs. A nodule lesion with yellowish-gray cut surface (a). The well-defined epithelial nests consisted of urothelium-like cells with clear to eosinophilic cytoplasm and longitudinal nuclear grooves (b). Cavities in epithelial islands were lined by a single layer of umbrella-like cell (c). Some cell nests resembled their counterparts in WNs (d). Original magnification x 400

Fig. 3

Immunophenotype of EOBTs. Epithelial cells exhibited strong activity for CK7 (a), rather than CK20 (b). Nuclear positivity for GATA3 (c). The graded intensity of CK5/6 (d) and 34βE12 staining (e) in cell nests. P63 decorated the majority of the epithelium (f). Original magnification x 400

Fig. 4

The immunohistochemical results of epithelial and stromal cells. A few of cavity-lined cells exhibited Uroplakin III positivity (a). Desmin immunopositivity confirmed smooth muscle nature of stromal cells (b). Stromal cells expressed ER (c) and PR (d). Tumor cells were negative for PAX8, p53, and p16 (e-g). The epithelium showed weak positivity for cyclinD1 (h). Original magnification x 200 (b, e-h) and x 400 (a, c, d)