Imaging characteristics of ovarian sclerosing stromal tumor

doi:10.21203/rs.3.rs-1494715/v1

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Imaging characteristics of ovarian sclerosing stromal tumor

https://doi.org/10.21203/rs.3.rs-1494715/v1

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Objectives To evaluate the specific imaging features of ovarian sclerosing stromal tumor (SST), improve its accuracy and specificity of imaging diagnosing, and prevent overestimation of malignancy and reduce unnecessary surgical procedures.

Methods Eight patients with magnetic resonance imaging (MRI) and six with computed tomography (CT) images were analyzed in this retrospectively observational study. All cases were confirmed by postoperative pathological examination as ovarian SST. Imaging and pathological features were analyzed.

Results All the 14 masses were showed cystic and solid components with outer surface of tumors contained a capsular and complete smooth rim. Eight tumors of MRI showed “lake-island” sign on T2 weighted imaging (T2WI). Two of the 6 CT cases found a flaky calcification. One case showed as a multiloculated cystic mass with irregularly thickened septae and tumor wall. The solid components in other 13 masses are comb- or wheel-like enhanced. After injection of contrast agent, the solid components in 8 cases (57.1%) appeared as early enhancement, while the other 6 cases (42.9%) appeared as progressive enhanced, and the cystic components of all cases had no enhancement in the whole course. Vascular flow signals or/and marked enhancement of blood vessels were found in 12 lesions (85.7%). Pathologic examination demonstrated pseudolobule patterns, round to spindle cells, collagenous areas, edematous hypocellular areas and prominent vasculatures.

Conclusions The results demonstrated that MRI with “lake-island” signs on T2WI and MRI/CT dynamic enhencement could play a critical role in making appropriate diagnosis preoperatively.

ovary

sclerosing stromal tumour

magnetic resonance imaging

computed tomography

Sclerosing stromal tumor (SST) is a very rare benign sex cord-stromal tumor (SCST) of the ovary, which was defined by Chalvardjian and Scully [1] in 1973 for the first time. More than 80% of SSTs were observed in young women in the 2nd and 3rd decades of life [2–6]. The most common presenting complaint is menstrual irregularity, abdominal pain and a lower abdominal mass [2, 7–10], which are not specific.

Histopathologically, SST has a particular pseudolobular architecture, which is formed by cellular nodules with hypocellular, edematous and collagenous or fibrous stroma [7, 11, 12]. Upon immunohistochemistry, the expression of angiogenic factors in SST makes the tumor rich in blood supply [2, 13]. The presence of solid component and high vascularity upon diagnostic imaging with magnetic resonance imaging (MRI) and/or computed tomography (CT) generally results in this tumor being suspected as borderline or malignant epithelial tumors and other SCST. Thus, accurate preoperative clinical diagnosis will be difficult. The definite diagnosis of SST is made based on post-operative pathological examination after oophorectomy, and laparoscopic surgery is seldom performed in SST cases. Therefore, accurate preoperative imaging diagnosis for SST can be helpful to prevent overestimation of malignancy, perform minimally invasive surgery and reduce unnecessary surgical procedures, especially in young women and children [10].

The present study review MRI/CT features of 14 cases of histologically confirmed ovarian SST and analyze the correlation between their imaging and pathological characteristics. The aims of this study are to evaluate the specific imaging features of ovarian SST, improve its accuracy and specificity of imaging diagnosing, and distinguish it from malignant tumors to avoid unnecessary surgery.

Patients

There were 14 cases (from 2005 to 2018) included in this retrospective study. The MRI/CT images of all cases were retrospectively reviewed by two experienced radiologists (G.H and G.W). When the diagnosis was inconsistent, a consensus was reached through discussion. The clinical details that were reviewed included age at the time of MRI/CT scanning, clinical presentation, location and size of the tumors (Table 1). The study protocol was approved by the Huazhong University of Science and Technology Union Shenzhen Hospital Institutional Review Board (The approval code: 2020012401).

Table 1

Clinical findings in cases of ovarian scleroding stromal tumor
Case No.	Age(years)	Clinical presentation	Side/size of tumor (cm)
MR01	27	Adnexal mass	LO/6.2×5.8
MR02	33	Pelvis mass	LO/8×7
MR03	15	Pelvis mass	RO/8×6
MR04	22	Pelvis mass	LO/8×6
MR05	24	Irregular menstruation	RO/7.2×5.6
MR06	14	Pelvis mass	RO/7.8×5.2
MR07	26	Adnexal cystic mass	LO/16.8×14.7
MR08	27	Adnexal mass, pelvic pain	RO/4.2×3.6
CT01	24	Adnexal mass	RO/8.6×5.9
CT02	27	-	RO/2.5×1.8
CT03	12	Pelvis mass	LO/11.6×10
CT04	18	Pelvis mass	LO/8.1×7.9
CT05	47	Pelvis mass	RO/10.3×9.3
CT06	22	Irregular menstruation	LO/6.6×4.9
Abbreviations: RO, right ovary; LO, left ovary.

Image Capture and Evaluation

Eight cases of MRI examinations were performed on 1.5T or 3.0T MR scanners. The sequences included T1 weighted imaging (T1WI), T2 weighted imaging (T2WI), and dynamic enhanced scanning after intravenous injection of gadolinium-containing contrast agent. Six cases of CT examinations were performed with plain scan and dynamic enhanced scanning after intravenous injection of iodine-containing contrast agent. The imaging characteristics that were collected included location, main component, calcification (CT cases), capsular rim, "Lake-island" sign, enhancement patterns, vascular flow/marked enhancement, comb-shaped wall nodules after enhancement, and without swollen lymph nodes around the mass.

Pathological presentations

The pathological characteristics that were reported included gross appearance, tumor size, alternating pattern and cell type of hypercellular and hypocellular areas, hemangiopericytoma-like vascular pattern, and histopathological abnormalities of the stroma, such as edema, cystic degeneration, and the presence of myxoid or necrotic tissue.

The 14 patients ranged in age from 12 to 47 years (Table 1). The mean age was 24.1 ± 8.8 years. The main clinical presentation was an adnexal or pelvis mass, 2 instances with irregular menstruation and 1 instance was normal. Only 1 case had pelvic pain. Among the 14 cases with SST of ovary, 7 of them located on the left ovary and 7 cases on the right. The tumors size varied from 2.5 to 16.8 centimetres in the largest diameter (Table 2).

Table 2

Imaging characteristics data of ovarian sclerosing stromal tumor
Imaging features	The number of cases	Mean age of patient (range, years)	Mean size of tumour (range, cm)
Location(L/R)	7/7	22.9(12–33)/25.4(15–47)	9.3(6.2–16.8)/7.0(2.5–10.3)
Main component (solid/cystic)	13/1	24(12–47)/26	8(2.5–11.6)/16.8
Calcification on CT	2	21(18–24)	8.4(8.1–8.6)
Capsular rim	14	24.1(12–47)	8.1(2.5–16.8)
"Lake-island" on T2WI	8	23.5(14–33)	8.3(4.2–16.8)
Progressive continual enhancement	6	23.8(12–33)	7.2(2.5-8)
Early-fast sustained enhancement	8	24.4(14–47)	8.9(4.2–16.8)
Vascular flow/marked enhancement	12	24.7(12–47)	7.9(4.2–11.6)
Comb-shaped wall nodule	13	24(12–47)	7.5(2.5–11.6)
Swollen lymph nodes	0	0	0
The mean size of the tumor was calculated by the largest diameter of the tumor.

Radiologically, plain CT scans showed mixed and low density, and T1WI showed hypointensity, while mixed and hyperintensity on T2WI. Thirteen masses (92.9%) were showed heterogeneously solid and cystic components, and 1 case (7.1%) predominantly cystic tumor. Two of the 6 CT cases (1/3) found a patchy calcification. In all cases, the outer surface of the tumor contained a capsular and complete smooth rim. Twelve cases of MRI/CT images showed a little ascites around the mass (85.7%). Two cases showed no ascites, but a small amount of light ascites were seen during surgery. Eight tumors (72.7%) showed scattered iso-hypointensity areas at the hyperintensity background within the neoplasm, i.e., “lake-island” sign, on T2WI. According to the pattern of dynamic enhancement, the solid components in 8 tumors (57.1%) appeared early-fast sustained enhancement, and the solid components of the other 6 cases (42.9%) showed progressive centripetal continual enhancement, while the cystic components of all cases had no enhancement in the whole course. During the delayed phases, the solid components in 13 masses were comb- or wheel-like enhanced, while the case MR07 showed as a multiloculated cystic mass with irregularly thickened septae and tumor wall. Vascular flow signals or/and marked enhancement of blood vessels were observed in 12 lesions (Table 2, Fig. 1–4). No pelvic or lumbo-aortic enlarged lymph nodes were observed.

On microscopic examination, the appearance of tumor was highly variable. All the tumors were well-circumscribed. Thirteen neoplasms were solid and cystic, and the other was predominantly cystic. Histologically, all the cases demonstrated pseudolobular appearance of cellular areas, collagenous and edematous hypocellular areas. In the cellular areas, round or oval-shaped and spindle cells predominated (Fig. 5). Twelve cases presented hemangiopericytoma-like vasculatures.

Ovarian SST is a considerably rare benign SCST that occurs commonly in young women during the childbearing age. According to previous reports, the patients’ ages ranged from 5 to 80 years (mean age 28 years) [1, 7, 11, 14]. In our 14 cases, patients were in a younger subgroup, ranging in age from 12 to 47 years (mean age 24.1 years). SST has variable and non-specific clinical presentations, usually include menstrual irregulatities, which was reported to disappear after surgical excision of the tumor [15, 16], adnexal mass and/or pelvic pain. Additionally, the tumors may, in some rare cases, cause masculinization, anovulation, infertility and Meigs’ syndrome [15, 17–19].

Histopathologically, SST is characterized by a cell-rich pseudolobular architecture in the edematous or fibrous stroma [7, 11]. The cell-rich areas consist mainly of spindle, round or oval-shape, and polygonal cells. The tumors also show hemangiopericytoma-like vascular pattern and express angiogenic factors [11, 13]. Occasional tumors present patchy calcification in the hypocellular areas [11, 19], which are in line with the case of CT01 and CT04 in this study.

Pathology and imaging findings can be mutually confirmed, i.e., imaging findings reflect pathological tissue structure and cellular distribution, and pathological changes can explain imaging findings at the molecular level. Previous studies demonstrated that the density or signal and enhancement patterns of SST were associated with the cellularity, vascularity, collagenous distribution and cystic or necrosis architecture observed in the histopathological examination of the tumor [6, 20]. In the present study, we found that most SSTs were the tumors with“lake-island” sign on T2WI and progressive centripetal/early-fast continual and comb- or wheel-like enhancement. These imaging findings reflect the tumor’s characteristic microscopic pattern in which the pseudo-separation of the cell-rich region is separated by the hypocellular region of the loose collagen and edematous connective tissue. In the T2WI “lake-island” sign, combining with the T1WI images, the scattered clusters and linear isointensity and/or hypointensity area on T2WI, and isointense to normal muscle on T1WI, indicates the corresponding area of cell-rich region, means “island”; while the hyperintensity area on T2WI, but hypointensity on T1WI, represents the edema and collagen stromal area, means “lake”. The SST is the only subtype of benign SCST that enhanced distinctly [9], which predict the hypervascularity of the tumor. Pathologically, prominent vascular and collagen components can explain the early and continual obviously enhancement of the image. In the artery phase after the administration of intravenous contrast material, the early and distinctive enhancement of the rim of the tumor was possibly due to the hypervascularity in this space. However, in the delayed phase, the area of prolonged and progressive enhancement observed in the inner zone of the mass was considered to be associated with the collagenized hypocellular area, which showed hyperintensity on T2WI [6]. The present imaging findings were in line with previous studies [6, 8, 20, 21]. Whether it showed early or prolonged enhancing, depending on whether the vascular component or collagen component was dominant in the tumor. In addition, one single case (case MR07) was diagnosed with ovarian myxoma due to the multiocular cystic imaging features, but postoperative pathology confirmed SST of the ovary. Lawrence and colleagues [22] reported 3 SSTs undergoing a transition to ovarian myxoma, which were in line with our case. This unusual histologic transformation could make the diagnosis more challenging.

The differential diagnoses of SSTs include other benign SCSTs, such as fibromas or thecomas, metastatic and malignant epithelial ovarian tumors. Most benign SCSTs are cytologically denser and more homogeneous than SST, similar to their differences in imaging. In addition, SST contains characteristic vasculature and is markedly enhanced, which is not available in fibromas or thecomas. Distinguished from malignant ovarian cancer is not always simple, given that the solid components of the tumor enhanced vividly for the dysregulation in vascular endothelial growth factor production. Nevertheless, no pelvic and para-aortic lymph nodes were swollen, which was an indirect sign suggesting the tumor is benign. Therefore, “Lake-island” signs on T2WI, comb- or wheel-like nodules with strong enhancement a peripheral hypointense rim and no swollen lymph nodes are the main findings of SST. NO signs of local or distal recurrences have been reported in our patients until now.

In summary, we have described and analyzed the MRI/CT findings and pathological features in ovarian SST, which may be helpful to improve the preoperative diagnosis of the tumor. Dynamic enhancement scanning plays the critical role in the diagnosis of the tumor by revealing the typical contrast enhancement pattern of the SST. T1WI combined with T2WI and the size of the pelvic or lumbo-aortic lymph nodes may be used as complementary imaging information to show the stromal component and identify with benign or malignant of the tumor, respectively. Combining all imaging findings helps the radiologists make a specific diagnosis of SST, which may lead to a less-invasive and unnecessary surgical procedure in young women and girls. Our findings identify distinctive imaging features of SST and expand our knowledge of their imageology.

SST: ovarian sclerosing stromal tumor; SCST: sex cord-stromal tumor; MRI: magnetic resonance imaging; CT: computed tomography; T1WI: T1 weighted imaging; T2WI: T2 weighted imaging.

Ethics approval and consent to participate

Current study was approved by the Huazhong University of Science and Technology Union Shenzhen Hospital in accordance with Declaration of Helsinki (The approval code: 2020012401). All the participants signed the informed consent prior to imaging.

Consent for publication

Not applicable.

Availability of data and materials

The datasets used and analysed during the current study are not publicly available due to the privacy protection of the subjects, but are available from the corresponding author on reasonable request.

Competing interests

The authors declare that they have no competing interests.

Funding

This work was supported by the Shenzhen Fund for Guangdong Provincial High-level Clinical Key Specialties (No. SZGSP013).

Authors’ contributions

Z.F.Z. and X.Q.C. contributed to writing the manuscript. Z.B.Z. and F.J.Z. and J.Y. prepared figures 1-5. G.Q.H. guaranteed the integrity of the entire study. All authors read and approved the final manuscript.

Acknowledgements

We would like to thank the whole study team at Shenzhen Kangning Hospital, Huazhong University of Science and Technology Union Shenzhen Hospital, The First Affiliated Hospital of Zhengzhou University and Affiliated Shenzhen Maternity ＆ Child Healthcare Hospita, Southern Medical University, for continuous support.

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No competing interests reported.

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You are reading this latest preprint version

Imaging characteristics of ovarian sclerosing stromal tumor

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Version 1

Abstract

Figures

Introduction

Materials And Methods

Patients

Image Capture and Evaluation

Pathological presentations

Results

Discussion And Conclusions

Abbreviations

Declarations

References

Additional Declarations

Status:

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