A Case Report: Ovarian Fibrothecoma with Minor Sex Cord Elements

Abstract

Introduction

Ovarian stromal tumors with minor sex cord elements are rare, and there are not specific imaging features to help in making the diagnosis.

Case Presentation

We report a case of this tumor in an 81-year-old woman who was referred to our hospital for constipation and a pelvic mass. Magnetic resonance imaging demonstrated a well-circumscribed mass and isointensity compared to the skeletal muscle on T1-weighted imaging (T1WI) and low signal intensity mixed with high signal ranges on T2-weighted imaging. Dynamic gadolinium-enhanced fat-suppressed T1WI revealed mild and increased enhancement of the peripheral area in the early and delayed phases, respectively. On diffusion-weighted imaging (DWI), a heterogeneously high signal intensity corresponding to the peripheral enhanced area was observed, and the apparent diffusion coefficient values of the high-intensity areas on DWI were low. Malignancy could be suspected, so the mass was surgically removed. Pathological assessment revealed a fibrothecoma with minor sex cord elements.

Conclusion

The tumor’s preoperative diagnosis is difficult, although the possibility of this rare tumor from atypical findings on DWI and/or dynamic contrast enhancement studies should be considered.

Introduction

An ovarian stromal tumor with minor sex cord elements is rare. It was first described by Young and Scully in 1983 as a predominantly fibromatous or thecomatous tumor, with minor sex cord elements occupying <10% of the tumor area [1]. To the best of our knowledge, only 20 cases have been reported [1–6], and no detailed imaging findings are available. Here, we present magnetic resonance imaging (MRI) findings of this rare tumor.

Case Presentation

An 81-year-old woman was referred to our hospital because of constipation and pelvic mass. She had undergone a total hysterectomy for uterine myoma and left salpingo-oophorectomy for an ovarian tumor 40 years ago. Information on when she had experienced menopause was unclear. She had a medical history of hypertension, dyslipidemia, and ischemic enteritis. Physical examination revealed that she had a pelvic mass, and transabdominal ultrasonography revealed the presence of a 10-cm round pelvic mass.

The levels of cancer antigen (CA) 125, CA19-9, and carcinoembryonic antigen were within normal limits. On unenhanced computed tomography (CT), a 10 × 10-cm mass demonstrating isodensity mixed with hypodensity with the skeletal muscle was observed at the center of the pelvis (Fig. 1a). MRI of the lower abdomen was performed using a 3-T MAGNETOM Skyra (Siemens Healthcare, Erlangen, Germany). On MRI, the mass was well circumscribed and revealed isointensity compared to the skeletal muscle on T1-weighted imaging (T1WI) and low signal intensity mixed with high signal ranges (arrows) on T2-weighted imaging (T2WI) (Fig. 1b, c). On dynamic gadolinium-enhanced fat-suppressed T1WI, the mass was continuous with the right ovarian artery and vein, suggesting that it originated from the right ovary and indicated mild enhancement of the peripheral area in the early phase and increased enhancement in the delayed phase (arrows) (Fig. 2d, e). The central area with enhancement reflected the abundant intratumoral vessels (curved arrow). Diffusion-weighted imaging (DWI) at a b-factor of 800 s mm⁻², the tumor revealed heterogeneously high signal intensity corresponding to the peripheral enhanced area (arrow) (Fig. 2f), and the apparent diffusion coefficient values of the high-intensity areas on DWI were 0.60–080 × 10⁻³ mm² s⁻¹. Thus, several fibrous tumors, including ovarian stromal tumors with minor sex cord elements, were suspected; malignancy could not be ruled out. We performed contrast-enhanced chest and abdominal computed tomography scans to examine the whole body. No distant metastasis was observed.

Fig. 1.

CT and MRI findings of ovarian fibrothecoma with minor sex cord elements. a Unenhanced CT indicating a relatively well-circumscribed mass measured 10 × 10 cm in diameter demonstrating isodensity mixed with hypodensity (arrow) with the skeletal muscle, in the pelvis. Axial (b) and sagittal (c) T2WI displaying a 9 × 10-cm well-defined mass as hypointense and hyperintense mixed (arrow). Dynamic gadolinium-enhanced fat-suppressed T1WI indicated mild enhancement of the peripheral area (arrow) in the early phase (d) and increased enhancement in the delayed phase (e). The central area with enhancement (curved arrow) reflected the abundant intratumoral vessels. f DWI at a b-factor of 800 s mm⁻², the tumor revealed heterogeneously high signal intensity (arrow) corresponding to the peripheral enhanced area.

Fig. 2.

Pathological findings of ovarian fibrothecoma with minor sex cord elements. a The mass measures 104 × 96 mm in diameter, and the cut section was white to light yellow in color. The sex cord elements are observed in the peripheral part of the mass (arrow). b Microphotogragh displaying fibroblast cells and theca cells (hematoxylin-eosin). c Sex cord-type cells with oval nucleus and minimal cytoplasm, comprising <1% of total tumor area, demonstrate a tubular structure and palisading arrangement (hematoxylin-eosin). The sex cord elements demonstrating immunoreactivity with calretinin (d) and inhibin-α (e) (immunohistochemistry).

She underwent abdominal surgery under general anesthesia, and the mass was removed. Right salpingo-oophorectomy was also performed. Pathological examination revealed a mass measuring 104 × 96 mm in diameter, and the cut section was white to light yellow in color (Fig. 2a). The sex cord elements are observed in the peripheral part of the mass (arrow). Microscopic examination revealed features of a fibrothecoma with minor sex cord elements (Fig. 2b, c). The sex cord cell aggregates with dense proliferation and angiogenesis resembling Sertoli-stromal cell aggregates were scattered at the peripheral sites of the mass and focally immunoreactive for calretinin (Fig. 2d) and inhibin-α (Fig. 2e), suggesting sex cord-stromal and fibrous neoplasms. A final diagnosis of fibrothecoma with minor sex cord elements in the right ovary was made.

Her postoperative recovery was favorable, so she was discharged from our hospital 7 days postoperatively. She was followed up at a gynecology clinic near her house. The patient did not exhibit signs of local recurrence or metastasis within 2 years.

Discussion

Minor sex cord elements are observed as small nests or tubules of cells resembling granulosa cells, Sertoli cells, or indifferent cells of the sex cord type. In the latest classification scheme for ovarian sex cord-stromal tumors (2014) of the World Health Organization, mixed sex cord-stromal tumors other than the Sertoli-Leydig cell type are classified as sex cord-stromal tumors (not otherwise specified). “Luteinized thecoma” is not categorized as a separate entity unless associated with “sclerosing peritonitis.” One group reported a case of 66-year-old woman with extraovarian fibroma with minor sex cord elements [6] and our case (81 year old woman) is unusual. Some investigators have reported cases of this entity; however, no detailed imaging findings are available. In particular, the only case report described MRI findings, demonstrating T1-hypointiense and T2-mixed-intense (solid and cystic) lobulated masses [7]. In this case, a post-contrast study (not a dynamic study) has reported diffuse enhancement of the ovarian mass, with few non-enhancing cystic areas, and DWI findings were not referred to. Therefore, this is the first case report to present MRI findings, including both dynamic studies and DWI, of this rare tumor. The mild and increased enhancement of the peripheral area in the early and delayed phases, respectively, on dynamic enhanced studies and high signal intensity on DWI corresponded to sex cord elements pathologically.

On MRI, the current mass demonstrated isointensity compared to the skeletal muscle on T1WI and low signal intensity mixed with mild high signal ranges on T2WI. In the dynamic study, dilated arteries were located inside the mass in the early phase, and the majority of the mass indicated faint enhancement, coexisting with several early and late well-enhanced parts that corresponded to the diffusion-restricted areas, suggesting the possibility of a fibrous tumor with a malignant component. Kitajima et al. [8] have reported that ovarian fibromas typically exhibit low signal intensity on T2WI and weak enhancement by contrast material, reflecting this pathological feature, while larger tumors demonstrate various MRI findings, which reflect varied degenerative changes, hemorrhagic infarction or necrosis, edematous change, and myxomatous change. Shinagare et al. [9] have reported that the enhancement of fibromas and fibrothecomas was significantly lower than that of the myometrium and fibroids at all time points. Most ovarian fibromas and fibrothecomas are isointense to hypointense to the uterine myometrium on T1- and T2-weighted images, and these ovarian tumors progress significantly less than uterine myometrium and fibroids. Here, although the uterine myometrium was not compared because of the post-hysterectomy status, the majority of the mass was similar to those of previous findings. However, intratumoral vessels and a few peripheral small parts showing well-enhanced and diffusion-restricted areas were atypical to those fibromas.

Pathologically, in our case, sex cord cell aggregates with dense proliferation resembling Sertoli-stromal cell aggregates were scattered at the peripheral sites of the mass. Yamano et al. [10] reported a case of ovarian Sertoli-stromal cell tumor, septa, the solid portion of which demonstrated marked enhancement on Gd-DTPA fat-suppressed T1WI. The current sex cord stromal components resembling Sertoli-stromal cells showed good enhancement on dynamic MRI, suggesting hypervascularity, which is consistent with their report. Moreover, the intratumoral vessels revealed on dynamic MRI might reflect several feeding arteries to the pathologically proven hypervascular components.

As mentioned above, this lesion exhibited heterogeneously high signal intensity on DWI, and the apparent diffusion coefficient values of the high-intensity areas were significantly low. Hence, this may be related to the distribution of substantial tumor cells, resulting in the restricted movement of water molecules. A previous report has noted that the majority of malignant sex cord-stromal tumors indicate high signal intensity on DWI, whereas most benign tumors demonstrate low or moderate signal intensity [11]. Although no malignant cells were detected in our case, performing laparotomy in cases where malignancy could not be ruled out confidently may be plausible.

Several cases of ovarian stromal tumors with minor sex cord elements coexisting with endometrial carcinoma have been reported in English literature [6, 11]. In these cases, endocrine function was due to luteinized thecoma cells or Leydig cells. Shilpa et al. [6] have reported a case in which functional activity was attributed to ovarian fibroma and minor sex cord elements because extensive search and fat staining did not reveal any thecoma cells. In the case of this tumor, careful follow-up, including the endometrium, is desired even after surgery.

Conclusion

The current rare tumor indicated various MRI findings and was strongly correlated with pathology. There are cases where the findings are suggestive of cancer but are not cancer. Atypical findings on DWI and/or dynamic contrast-enhancement study as “pure ovarian fibroma” might be a key to list this rare tumor as one of the differential diagnoses. Therefore, the addition of these studies to conventional imaging is recommended in the case of relatively large ovarian solid tumors. The CARE Checklist has been completed by the authors for this case report, attached as online supplementary material (for all online suppl. material, see https://doi.org/10.1159/000534798).

Statement of Ethics

This report complies with the guidelines for human studies and includes evidence that the research was conducted ethically in accordance with the World Medical Association Declaration of Helsinki. The authors have no ethical conflicts to disclose. Written informed consent was obtained from the patient for publication of this case report and any accompanying images. Ethical approval is not required for this study in accordance with local or national guidelines. This retrospective review of patient data did not require ethical approval in accordance with local/national guidelines.

Conflict of Interest Statement

The authors have no conflicts of interest to declare.

Funding Sources

This work was supported by JSPS KAKENHI (Grant No. 22K07757).

Author Contributions

Concept and design: K.K. and T.M.; acquisition of data: R.M., T.W., and N.O.; drafting of the manuscript: K.K.; and critical revision of the manuscript for important intellectual content: T.M.: All authors approved final version of manuscript.

Funding Statement

This work was supported by JSPS KAKENHI (Grant No. 22K07757).

Data Availability Statement

All data generated or analyzed during this study are included in this article and its online supplementary material files. Further inquiries can be directed to the corresponding author.