Abstract
Introduction
Ovarian immature teratomas (ITs) are rare malignant ovarian tumors predominantly affecting young women and adolescents. Distinguishing these lesions preoperatively is clinically challenging. This study aimed to describe the clinical and sonographic features of ITs and evaluate the correlation between sonographic manifestations and pathological grades.
Material and Methods
This retrospective study reviewed the medical records of patients with pure ovarian ITs treated at Peking Union Medical College Hospital between 2017 and 2025. Two experienced gynecologic sonologists independently reassessed the original ultrasound images, recorded the sonographic features and O‐RADS category of each mass, and classified the tumors into four predefined sonographic patterns based on imaging pattern recognition. Associations between sonographic features and pathological grade were assessed using Fisher's exact test or Spearman's rank correlation analysis.
Results
Thirty patients with histologically confirmed pure ovarian ITs were included, with a median age of 25.2 years (range 7.0–39.0 years). Serum AFP elevation was observed in 56.7% of patients. Pathological grades were distributed as grade 1 (36.7%), grade 2 (36.7%), and grade 3 (26.7%). FIGO stage was predominantly stage IA (46.7%) and IC (50.0%). The median maximum tumor diameter was 16.7 cm (range 5.1–28.2 cm). Grayscale ultrasonography demonstrated solid components in all tumors, with 9 (30.0%) being purely solid and 21 (70.0%) being cystic‐solid. Tumor rupture was identified during surgery in 77.8% of patients presenting with solid morphology on ultrasonography. All tumors demonstrated the “pebbled mosaic sign” within solid components, manifested as heterogeneous echogenicity on a hypoechoic grayscale background, with scattered hyperechoic foci, localized fatty‐like homogeneous hyperechoic areas, and anechoic vesicles. Moderate vascularity was observed in 76.7% of tumors. Minimal and abundant vascularity were seen in 20.0% and 3.3% of tumors, respectively. Solid morphology was associated with higher pathological grade.
Conclusions
The “pebbled mosaic sign” describes the characteristic heterogeneous sonographic appearance of the solid component of ovarian ITs. Solid tumors classified as pattern 1 may be associated with a higher pathological grade.
Keywords: immature teratoma, ovarian germ cell tumor, pathological grade, ultrasound
This study characterizes heterogeneous mottled grayscale ultrasound echoes of ovarian immature teratoma as the “pebbled mosaic sign,” noting solid lesions correlate with advanced pathological grades. Preoperative identification of immature tissue informs operative stratification.
Abbreviations
- AFP
α‐fetoprotein
- CA125
cancer antigen 125
- CA19‐9
carbohydrate antigen 19–9
- IOTA
International Ovarian Tumor Analysis
- IQR
interquartile range
- IT
immature teratoma
- MT
mature teratoma
- O‐RADS
Ovarian‐Adnexal Reporting and Data System
Key message.
The “pebbled mosaic sign” manifests as heterogeneous mottled grayscale echoes in ovarian immature teratomas; solid‐pattern lesions correlate with higher pathological grades, and accurate preoperative recognition guides surgical decision‐making.
1. INTRODUCTION
Ovarian immature teratomas (ITs) are rare tumors, accounting for approximately 3% of ovarian malignancies and 35%–38% of malignant ovarian germ cell tumors. 1 They predominantly affect adolescents and young adults aged 10–30 years. 2 , 3 The prognosis of patients with early‐stage disease is generally excellent. 3 Tumor stage, grade, and completeness of surgical resection are prognostic risk factors. 4 Because most patients are young and have not completed childbearing, surgical management requires a careful balance between oncological safety and fertility preservation. Cystectomy may increase the risk of intraoperative tumor rupture, surgical upstaging, and recurrence compared with salpingo‐oophorectomy. 5 , 6 Conversely, salpingo‐oophorectomy may result in unnecessary loss of ovarian tissue and reproductive potential when a lesion suspected to be malignant is ultimately confirmed to be benign. Therefore, the preoperative determination of tumor characteristics is crucial for surgical decision‐making.
Ovarian ITs typically present as large, unilateral, encapsulated masses that are cystic‐solid or predominantly solid. 7 , 8 Clinical manifestations range from a palpable abdominal mass and nonspecific abdominal discomfort to acute abdomen resulting from ovarian torsion or tumor rupture. Serum tumor markers such as α‐fetoprotein (AFP), cancer antigen 125 (CA125), and carbohydrate antigen 19‐9 (CA19‐9) may be elevated or normal. 9 Histopathological examination reveals characteristic mixtures of immature neuroectodermal and blastemal components with heterologous mesodermal and endodermal tissues at varying stages of maturation. The complex polyembryonic components and atypical clinical features often make ITs difficult to differentiate from mature teratomas (MTs) or other ovarian malignancies. Due to nonspecific clinical manifestations and the limited diagnostic value of tumor markers, the preoperative diagnosis of ITs remains challenging.
Ultrasonography is the most commonly used screening method for adnexal lesions. The standardized methodology developed by the International Ovarian Tumor Analysis (IOTA) group, 10 including the Simple Rules and logistic regression models, significantly enhances the accuracy and reproducibility of adnexal mass assessment 11 ; however, evidence regarding its application in ovarian malignant germ cell tumors remains limited. The Ovarian‐Adnexal Reporting and Data System (O‐RADS) also provides a standardized lexicon for adnexal lesion characterization 12 ; nevertheless, it lacks standardized criteria for describing the echogenicity of solid components. Moreover, non‐epithelial ovarian tumors accounted for only approximately 2% of the cohorts used to establish and validate the scoring system. 13 Recent retrospective studies suggested that heterogeneous echogenicity of solid components is a characteristic sonographic feature of ITs; however, current studies remain limited by small sample sizes, heterogeneous imaging descriptions, and insufficient sonographic–pathological correlation. 14 , 15
In this study, we retrospectively analyzed the clinical and sonographic features of ITs and proposed distinctive ultrasound signs to enhance preoperative diagnostic accuracy. We further investigated the pathological basis of these signs and evaluated their associations with pathological grade.
2. MATERIAL AND METHODS
2.1. Study population
This was a retrospective single‐center study performed at Peking Union Medical College Hospital, Beijing, China. The study was approved by the ethics committee of Peking Union Medical College Hospital (NO: I‐24PJ1680). Patients who underwent surgery for ovarian tumors with pathologically confirmed IT between June 2017 and February 2025 were included. Mixed germ cell tumors and ITs with primitive neuroectodermal tumors were excluded. Ultimately, 30 patients with complete preoperative ultrasonographic images or videos were included. The screening process is illustrated in Figure S1.
2.2. Ultrasound and pathological examination
Preoperative transvaginal or transabdominal ultrasound examinations were performed by experienced gynecologic sonologists using the EPIQ 7 ultrasound system (Philips, Eindhoven, The Netherlands), the Mindray Resona R9 (Mindray, Shenzhen, China), and the Voluson E10 (GE Healthcare, Zipf, Austria). Ultrasound images and data were extracted from the ultrasound image workstation. Clinicopathological information was extracted from the hospital information system and de‐identified.
Two experienced sonologists (N.S. and Z.L.) independently reassessed the ultrasound images and videoclips. Any discrepancies were resolved by consensus review with a third sonologist (Z.Q.). Mass morphology, vascularity, and O‐RADS risk stratification were described according to the IOTA terminology. 16 Cystic‐solid tumors were defined as lesions containing a measurable solid component, while solid tumors were defined as lesions composed of ≥ 80% solid tissue on a two‐dimensional section. Blood flow was graded semi‐quantitatively via color score based on the highest degree of vascularization observed within the lesion: 1 (no color or power Doppler signals), 2 (minimal color or power Doppler signals), 3 (moderate color or power Doppler signals), and 4 (abundant color or power Doppler signals). Pattern recognition was performed by visually assessing the overall sonographic morphology of each tumor and classifying it into one of four predefined patterns adapted from Landolfo et al. (Table 1). 14
TABLE 1.
Predefined sonographic patterns used for pattern‐recognition classification of ovarian immature teratoma.
| Pattern | Description 14 |
|---|---|
| 1 | A purely solid tumor, that is, a tumor consisting of ≥80% solid tissue |
| 2 | A cystic tumor with a solid component that seemed to arise from the cyst wall but did not protrude into the cyst cavity like a papillary projection would |
| 3 | A cystic tumor with a solid component that seemed to protrude into the cyst cavity like a large papillary projection |
| 4 | A multilocular‐solid tumor with solid tissue entrapped among septa |
We defined a new term, the “pebbled mosaic sign,” to describe a distinctive sonographic feature of the solid component of ITs, characterized by pebbled mosaic‐like heterogeneous, mottled echogenicity. The sign manifested as a hypoechoic background on grayscale images interspersed with multiple sonographic elements: (1) scattered hyperechoic foci with posterior acoustic shadowing, (2) localized fatty‐like homogeneous hyperechoic areas demonstrating mild posterior attenuation, and (3) anechoic vesicles of varying sizes, either embedded within the interstitial matrix of the solid component or protruding from the peripheral margins of the solid component into the cystic lumen.
Pathologic diagnosis was reviewed and re‐evaluated by two experienced pathologists (X.S. and Y.Z.), and the pathological grades were reconfirmed. Grade 1 is characterized by ≤1 immature neuroepithelial focus per low‐power field (40×); grade 2 by >1 and ≤3 foci per low‐power field; and grade 3 by >3 foci per low‐power field. 17 Complete surgical staging was defined as peritoneal cytology examination, peritoneal biopsy, omentectomy or omental biopsy, with or without lymph node dissection. Fertility‐sparing surgery was defined as the preservation of at least one ovary and the uterus.
2.3. Statistical methods
Continuous variables are presented as median (range) [interquartile range (IQR)], and categorical variables are presented as n (%). Associations between categorical variables were assessed using Fisher's exact test, whereas correlations between continuous variables were evaluated using Spearman's rank correlation analysis. Spearman's rank correlation coefficient (ρ) values of >0.3, >0.5, and >0.7 indicate weak, moderate, and strong correlations, respectively. 18 Two‐sided p < 0.05 was considered statistically significant. Statistical Package for the Social Sciences software version 26.0 (IBM Corporation, Armonk, NY, USA) and R 4.3.2 were used for statistical analysis.
3. RESULTS
Thirty patients with a pathological diagnosis of pure ovarian IT were included in this study. The clinical and pathological features are shown in Table 2. The median age was 25.2 years (range 7.0–39.0; IQR 19.0–31.8 years), and 76.7% (23/30) of patients were nulliparous. Abdominal discomfort was the most common presentation, occurring in 66.7% (20/30) of patients, while 16.7% (5/30) presented with a palpable mass and 16.7% (5/30) were asymptomatic. Serum AFP levels were elevated in 56.7% (17/30) of patients, CA125 in 66.7% (20/30), and CA19‐9 in 50.0% (15/30). Surgical exploration revealed preoperative tumor rupture in 7 patients. Among the 29 (96.7%) patients who underwent fertility‐sparing surgery, 21 received salpingo‐oophorectomy and 8 received cystectomy. Of the 28 patients who underwent intraoperative frozen section examination, 67.9% (19/28) were definitively diagnosed with or strongly suspected to have IT, while 32.1% (9/28) were diagnosed with MT. Of all patients, one patient was diagnosed with stage IIIC disease, while the remaining 29 patients had stage I disease, including 14 (46.7%) with stage IA, 9 (30.0%) with stage IC1, and 6 (20.0%) with stage IC2. Pathological grade 1, grade 2, and grade 3 accounted for 36.7% (11/30), 36.7% (11/30), and 26.7% (8/30), respectively. The median follow‐up time was 20.9 months (range 1.6–95.0 months), during which two patients (one with stage IC2, grade 3 disease and one with stage IC1, grade 3 disease) developed malignant recurrence.
TABLE 2.
Clinical and pathological characteristics of ovarian immature teratoma.
| Characteristic | Median (range) [IQR] or N (%) |
|---|---|
| Age (years) | 25.2 (7–39) [19.0–31.8] |
| Nulliparous | 23 (76.7%) |
| Symptomatology | |
| Abdominal discomfort | 20 (66.7%) |
| Palpable mass | 5 (16.7%) |
| No symptoms | 5 (16.7%) |
| Serum tumor markers | |
| Elevated AFP (normal ≤20 ng/mL) | 17 (56.7%) |
| Elevated CA125 (normal ≤35 U/mL) | 20 (66.7%) |
| Elevated CA19‐9 (normal ≤34 U/mL) | 15 (50.0%) |
| AFP (ng/mL) | 24.8 (1.6–4541.0) [8.7–58.6] |
| CA125 (U/mL) | 61.7 (10.4–556.7) [27.8–126.0] |
| CA19‐9 (U/mL) | 34.7 (2.0–482.0) [10.6–105.3] |
| Surgical procedure | |
| Fertility‐sparing surgery staging | 6 (20.0%) |
| Non‐fertility‐sparing surgery staging | 1 (3.3%) |
| Unilateral salpingo‐oophorectomy | 15 (50.0%) |
| Cystectomy | 8 (26.7%) |
| Preoperative tumor rupture | |
| Yes | 7 (23.3%) |
| No | 23 (76.7%) |
| Frozen pathology a | |
| IT | 12 (42.9%) |
| Suspected IT | 7 (25.0%) |
| MT | 9 (32.1%) |
| Pathological grade | |
| 1 | 11 (36.7%) |
| 2 | 11 (36.7%) |
| 3 | 8 (26.7%) |
| FIGO stage | |
| IA | 14 (46.7%) |
| IB | 0 (0.0%) |
| IC1 | 9 (30.0%) |
| IC2 | 6 (20.0%) |
| IC3 | 0 (0.0%) |
| IIIC | 1 (3.3%) |
| Outcome | |
| No relapse | 28 (93.3%) |
| Recurrence | 2 (6.7%) |
Data available for 28 patients.
Ultrasonography identified bilateral ovarian masses in 7 patients, demonstrating a distinct pattern of unilateral large solid masses with contralateral cystic lesions. Pathological examination confirmed unilateral ITs with concurrent benign contralateral tumors, including four MTs, two endometriotic cysts, and one follicular cyst. The sonographic features are summarized in Table 3. The median maximum diameter of ovarian ITs was 16.7 cm (range 5.1–28.2 cm; IQR 13.0–20.7 cm). All tumors contained solid components and were classified according to IOTA terminology as cystic‐solid in 21 cases (70.0%), including 5 unilocular‐solid and 16 multilocular‐solid tumors, and solid tumors in 9 cases (30.0%). The cystic‐solid tumors were generally regular and well circumscribed, whereas all solid masses were irregular and markedly lobulated. All seven tumors with preoperative rupture exhibited solid morphology, accounting for 77.8% (7/9) of the solid masses (Figure 1).
TABLE 3.
Ultrasonographic characteristics of ovarian immature teratomas.
| Characteristic | Median (range) [IQR] or N (%) |
|---|---|
| Maximum tumor diameter (cm) | 16.7 (5.1–28.2) [13.0–20.7] |
| Tumor type (IOTA) | |
| Cystic | 0 (0.0%) |
| Unilocular cyst | 0 |
| Multilocular cyst | 0 |
| Cystic‐solid | 21 (70.0%) |
| Unilocular‐solid cyst | 5 |
| Multilocular‐solid cyst | 16 |
| Solid | 9 (30.0%) |
| Ultrasound pattern | |
| Pattern 1 | 9 (30.0%) |
| Pattern 2 | 3 (10.0%) |
| Pattern 3 | 12 (40.0%) |
| Pattern 4 | 6 (20.0%) |
| O‐RADS category | |
| 4 | 7 (23.3%) |
| 5 | 23 (76.7%) |
| Hyperechogeneity and posterior acoustic shadowing | |
| Yes | 30 (100.0%) |
| No | 0 (0.0%) |
| Homogeneous hyperechogenicity | |
| Yes | 30 (100.0%) |
| No | 0 (0.0%) |
| Color score | |
| 1 | 0 (0.0%) |
| 2 | 6 (20.0%) |
| 3 | 23 (76.7%) |
| 4 | 1 (3.3%) |
FIGURE 1.
Grayscale, Doppler, gross pathology, and cut‐surface images of immature teratoma. (A–D) A cystic‐solid mass with grade 1 tumor, and (E–H) a solid mass with grade 3 tumor. The white arrow indicates the site of spontaneous tumor rupture.
Using pattern recognition, 9 solid tumors were classified as pattern 1, consistent with the solid mass category defined by IOTA. The remaining 21 cystic‐solid tumors were classified as patterns 2–4: three had a substantial solid component arising from the cyst wall without protrusion into the cyst cavity as a papillary projection; 12 had a solid component protruding into the cyst cavity, resembling a large papillary projection; and six were multilocular‐solid masses with solid tissue entrapped between the septa (Figure 2). According to the IOTA color score, Doppler signals were detected in all tumors: six (20.0%) showed minimal vascularity (color score 2), 23 (76.7%) showed moderate vascularity (color score 3), and one (3.3%) showed abundant vascularity (color score 4). According to the O‐RADS classification, seven tumors (23.3%) were classified as O‐RADS category 4, and 23 (76.7%) as category 5.
FIGURE 2.
Grayscale ultrasound images of ovarian immature teratomas characterized by pattern recognition. (A–C) Pattern 1, described as a purely solid tumor. (D–F) Pattern 2, described as a cystic tumor with a solid component originating from the cyst wall but not protruding into the cyst cavity, akin to a papillary projection. (G–I) Pattern 3, described as a cystic tumor with a solid component protruding into the cyst cavity resembling a large papillary projection. (J–L) Pattern 4, described as a multilocular‐solid tumor with solid tissue entrapped among septa.
All tumors exhibited the “pebbled mosaic sign” (Figure 3A–C, Video S1), in which the solid component displayed heterogeneous, mottled echogenicity composed of a mixture of hyperechoic areas and anechoic vesicles against a hypoechoic background. Specifically, 9 tumors primarily exhibited hypoechoic components, 4 predominantly showed hyperechoic components, and 17 displayed a roughly equal proportion of hypoechoic and hyperechoic areas. Additionally, a representative CT image of an IT is shown in Figure 3D, demonstrating heterogeneous high‐ and low‐density components within the solid component of a large pelvic mass. The morphologic features of the “pebbled mosaic sign” were illustrated by analogy to an image of a pebbled path (Figure 3E). In combination with gross pathology (Figure 3F) and histopathology (Figure 3G,H), the solid component was found to be predominantly composed of immature neuroepithelial tissue. Within this solid component, scattered hyperechoic foci with acoustic shadowing and uniformly hyperechoic regions with mild acoustic attenuation corresponded to calcified and fatty components of the teratoma, respectively. The vesicles appearing within and/or at the margin of the solid component presented as one or more anechoic lesions of varying sizes, ranging from <1 cm to 6 cm in diameter (Figure 4, Video S2). The fluid within these vesicles was typically clear and thin. Pathologically, the walls of these vesicles were lined by benign squamous epithelium, consistent with epidermoid cysts.
FIGURE 3.
Sonographic features and pathologic manifestations of the “pebbled mosaic sign.” (A–C) “Pebbled mosaic sign” in grayscale ultrasound images. (D) CT showed a high‐density component (calcification, white arrow) and a low‐density component (fat, yellow triangle) within the mass. (E) A picture of a pebbled path, provided as a visual analogy for the heterogeneous mottled echotexture. (F) Gross pathology of a grade 3 immature teratoma showed complex intra‐tumoral composition, including fat, calcifications, and cystic areas within solid regions. The histopathological images demonstrate multiple germ layer components, including (G) columnar epithelium (blue arrow) and its associated tubular structure (blue triangle), (H) fat tissue (yellow triangle), calcification (white arrow), hair (black arrow), and (I) immature neuroepithelium (black square).
FIGURE 4.
Vesicles in the “pebbled mosaic sign.” (A–C) Vesicles appearing within or at the margins of the solid components in grayscale ultrasound images of ovarian immature teratoma. (D) Three‐dimensional imaging showing multiple round cystic areas within the tumor. (E) Gross pathology shows thin‐walled sacs protruding into the cystic cavity at the margins of the solid areas, and (F) variably sized vesicles distributed within the solid areas.
Table 4 presents the associations between sonographic features and pathological grades. Because pattern 1 corresponded to solid tumors, whereas patterns 2–4 represented cystic‐solid masses, the latter three patterns were combined for analysis. Maximum diameter was moderately and inversely correlated with pathological grade (Spearman's ρ = −0.430, p = 0.02). Tumor morphology was significantly associated with pathological grade (p < 0.001): 7 of the 9 solid tumors classified as pattern 1 were associated with grade 3, whereas only one of the 21 cystic‐solid tumors classified as patterns 2–4 was grade 3. No statistically significant associations were observed between pathological grade and color score (p = 0.18) or O‐RADS category (p = 0.08).
TABLE 4.
Associations between sonographic features and pathological grade.
| Characteristic | N or median (range) [IQR] | Grade 1 | Grade 2 | Grade 3 | Statistical value | p |
|---|---|---|---|---|---|---|
| Maximum tumor diameter (cm) | 16.7 (5.1–28.2) [13.0–20.7] | ρ = −0.430 | 0.02 | |||
| Tumor type (IOTA)/pattern | Not applicable a | <0.001 | ||||
| Solid/pattern 1 | 9 | 1 | 1 | 7 | ||
| Cystic‐solid/pattern 2, 3 and 4 | 21 | 10 | 10 | 1 | ||
| Color score | Not applicable a | 0.18 | ||||
| ≤2 | 6 | 2 | 4 | 0 | ||
| ≥3 | 24 | 9 | 7 | 8 | ||
| O‐RADS category | Not applicable a | 0.08 | ||||
| 4 | 7 | 2 | 5 | 0 | ||
| 5 | 23 | 9 | 6 | 8 |
The statistical method was the Fisher exact probability test, without statistical specific test value. ρ: Spearman's rank correlation coefficient.
4. DISCUSSION
Ovarian ITs typically occur in children and young women, manifesting as large cystic‐solid or predominantly solid pelvic masses. Current research on sonographic characteristics remains limited. We proposed the term “pebbled mosaic sign” as a composite sonographic descriptor of the heterogeneous internal echotexture of the solid component of ovarian ITs. This sign integrates several recurrent sonographic elements into a structured pattern that may facilitate preoperative recognition of ovarian ITs.
Most ovarian ITs occur in patients aged ≤ 30 years, 19 , 20 with a median age of 25.2 years in our study. The clinical presentations are nonspecific, and only about half of our patients had elevated AFP levels. Both the European Society of Gynecological Oncology 21 and the Malignant Germ Cell International Consortium group 1 recommend complete en‐bloc oophorectomy for unilateral ITs to minimize the risk of tumor rupture and residual disease. Therefore, accurate preoperative differentiation of ITs from MTs and epithelial tumors is crucial because it directly influences surgical approach, particularly in young patients, for whom the choice between cystectomy and salpingo‐oophorectomy requires careful consideration. Intraoperative frozen‐section examination may aid intraoperative decision‐making. However, its accuracy in diagnosing ovarian ITs may be limited by the marked histological heterogeneity of these tumors and sampling constraints. Reported concordance rates between frozen‐section and permanent paraffin‐embedded diagnoses of ovarian ITs range from 50.0% to 78.4%. 22 , 23 In our study, 9 of 28 tumors (32.1%) assessed by frozen section were interpreted as MTs. Therefore, frozen‐section findings should be interpreted in conjunction with the patient's clinical characteristics and preoperative imaging features. A high preoperative suspicion of IT may help guide appropriate tissue sampling and surgical planning, particularly when fertility preservation is being considered.
Ultrasound is a rapid and non‐invasive imaging modality. Ovarian ITs typically appear as large masses with a predominantly solid component and complex heterogeneous echotexture. 14 , 24 According to the O‐RADS classification, all tumors in our cohort were categorized as intermediate‐ or high‐risk lesions. Of these, 23.3% were assigned to O‐RADS 4, which corresponds to a broad malignancy‐risk range of 10% to <50%. Although O‐RADS appropriately indicated malignant potential, its broad risk categories and lack of histological specificity may limit precise characterization of ovarian ITs. We therefore proposed the “pebbled mosaic sign” as a complementary pattern‐recognition descriptor that may increase preoperative suspicion of ovarian ITs. This sign refers to heterogeneous echogenicity within the solid components, characterized by scattered punctate hyperechoic foci with posterior acoustic shadowing, fatty‐like homogeneous hyperechoic areas demonstrating mild posterior attenuation, and anechoic cystic vesicles of varying sizes. Similar sonographic features were observed in all patients in our cohort and in previous retrospective studies. 14 This complex echotexture may reflect the admixture of mature and immature tissues derived from multiple germ layers, particularly the heterogeneous distribution of calcification, fat, immature tissue, and cystic structures.
In ITs, calcification is characterized by varying sizes of calcified cartilage and bone fragments scattered throughout the tumor, 25 appearing as hyperechoic areas with acoustic shadowing on ultrasound. In contrast to the focal distribution of coarse or serrated calcifications typically seen in MTs, calcifications in ITs tend to be more randomly and diffusely distributed. 7 , 26 Fat in ITs is also diffusely distributed and interspersed within the solid component, 27 , 28 appearing as focal hyperechoic areas with mild posterior acoustic attenuation on ultrasound. In contrast, fat components within MTs typically aggregate into spherical structures, producing characteristic sonographic signs such as the “echogenic white ball,” “fat fluid levels/mushroom cap sign,” and “pure fat patterns/completely hyperechoic lesion”. 27 , 29 , 30 This pattern of fat distribution in ITs may be related to mesenchymal differentiation into adipocytes and varying degrees of tissue maturation. 26 These scattered foci of calcification and fat are the focus of the differentiation between IT and MT 31 , 32 , 33 ; however, ultrasound has limited sensitivity for detecting small fatty components. Additional CT or MRI evaluation may provide complementary information when available. The cystic components of MTs predominantly contain fatty sebaceous fluid. 34 In contrast, the vesicles of ITs predominantly show CT attenuation and MRI signal intensity similar to simple serous or mucinous fluid. 35 On gross pathology, the cut surface exhibits a multinodular structure, 34 and pathological examination reveals that the vesicle walls are lined by benign squamous epithelium resembling epidermoid cyst structures.
Previous CT and MRI studies have suggested that the amount and distribution of solid components may help distinguish ITs from MTs and other fat‐containing adnexal masses. 26 , 30 , 36 Although an increased amount of solid tissue has been associated with malignant potential, the relationship between solid component volume and histological grade remains uncertain. 32 In our study, solid morphology classified as pattern 1 was significantly associated with a higher pathological grade, warranting particular clinical attention due to the increased recurrence risk associated with higher‐grade disease. 37 Spontaneous rupture was also confirmed in seven of the nine solid tumors, indicating that the possibility of rupture should be considered when planning surgery for solid masses highly suggestive of IT. When IT is strongly suspected, complete surgical resection should be considered while minimizing the risk of tumor rupture. Maximum tumor diameter showed a moderate inverse correlation with pathological grade, whereas neither color score nor O‐RADS category was significantly associated with grade. Given the small sample size and limited number of tumors within each grade category, these findings should be regarded as exploratory and require validation in larger cohorts.
The main strength of our study was the comparatively large sample size for this rare pathological tumor type. All patients included had pure ovarian ITs, ensuring that the ultrasound findings were representative of this specific histological entity. Nevertheless, several limitations should be acknowledged. As ultrasound is a dynamic modality, stored static images from our retrospective cohort may not fully capture the complete characteristics of each lesion. Technical parameters, including pulse repetition frequency, could not be modified to optimize Doppler‐score evaluation. Furthermore, reviewers were aware of the diagnosis, which may have introduced assessment bias. Future prospective studies with blinded reviewers and expanded sample cohorts are needed to validate these findings.
5. CONCLUSION
The “pebbled mosaic sign” may serve as a complementary recognition descriptor for ovarian IT in young patients with large unilateral cystic‐solid or solid O‐RADS 4 or 5 adnexal masses. Its presence may facilitate diagnosis by integrating clinical characteristics, serum tumor markers, and cross‐sectional imaging, thereby guiding surgical management and intraoperative sampling. Solid tumors classified as pattern 1 with heterogeneous echogenicity may indicate higher pathological grades. Additionally, vigilance for spontaneous tumor rupture in solid masses is warranted, and this risk should be integrated into surgical planning and decision‐making.
AUTHOR CONTRIBUTIONS
Tianyu Zhang: Data curation, Formal analysis, Methodology, Writing‐original draft. Jie Yang: Methodology, Formal analysis, Project administration, Writing‐review & editing. Xiaohua Shi: Data curation, Validation. Zhenzhen Liu: Data curation, Validation. Dan Wang: Data curation, Writing‐review & editing. Yang Zhou: Data curation, Validation. Na Su: Conceptualization, Data curation, Methodology, Writing‐review & editing. Jiaxin Yang: Conceptualization, Funding acquisition, Supervision.
FUNDING INFORMATION
This study is supported by the National Key Research and Development Program of China (2025YFC2708301) and the National High Level Hospital Clinical Research Funding (2026‐PUMCH‐A‐019).
CONFLICT OF INTEREST STATEMENT
The authors declare no conflict of interest.
ETHICS STATEMENT
This retrospective study was approved by the Ethics Committee of Peking Union Medical College Hospital (NO: I‐24PJ1680, Approval Date: August 11, 2024). All procedures were carried out following the Declaration of Helsinki. Written informed consent to participate in the study was waived by the Peking Union Medical College Hospital ethics committee due to the retrospective nature of the study.
Supporting information
Figure S1. Flow chart of the screening process.
Video S1. Grayscale ultrasound image of the “pebbled mosaic sign.” The mass was predominantly solid with mixed echoes. Scattered areas of hyperechoic distribution with acoustic shadowing or sound attenuation were seen within the tumor, mixed with multiple echogenic cystic cavities of varying sizes. The pathologic diagnosis was IT grade 3, and the stage was IC2. Creator: Na Su.
Video S2. Grayscale ultrasound image of the various vesicles in the “pebbled mosaic sign.” This is a cystic‐solid mass. At the periphery of the solid region, multiple vesicles of varying sizes, exhibiting anechoic signals, are clustered and protrude into the cystic cavity, forming a “capsule in capsule” structure. The pathologic diagnosis was IT grade 1, and the stage was IA. Creator: Na Su.
ACKNOWLEDGMENTS
We would like to thank Dr. Richard Lee for helping with language refinement and providing the native English terminology for the term “pebbled mosaic.” We extend our thanks to Prof. Yang Xiang, Prof. Shuiqing Ma, Prof. Huimei Zhou, and Prof. Tong Ren from Peking Union Medical College Hospital for their support with the surgical images, and to Prof. Zhenhong Qi from Peking Union Medical College Hospital for carefully reviewing and verifying the ultrasound images. No artificial intelligence technologies or large language models were employed in the preparation of this manuscript.
DATA AVAILABILITY STATEMENT
All data generated or analyzed during this study are included in this published article and its supplementary information files.
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Supplementary Materials
Figure S1. Flow chart of the screening process.
Video S1. Grayscale ultrasound image of the “pebbled mosaic sign.” The mass was predominantly solid with mixed echoes. Scattered areas of hyperechoic distribution with acoustic shadowing or sound attenuation were seen within the tumor, mixed with multiple echogenic cystic cavities of varying sizes. The pathologic diagnosis was IT grade 3, and the stage was IC2. Creator: Na Su.
Video S2. Grayscale ultrasound image of the various vesicles in the “pebbled mosaic sign.” This is a cystic‐solid mass. At the periphery of the solid region, multiple vesicles of varying sizes, exhibiting anechoic signals, are clustered and protrude into the cystic cavity, forming a “capsule in capsule” structure. The pathologic diagnosis was IT grade 1, and the stage was IA. Creator: Na Su.
Data Availability Statement
All data generated or analyzed during this study are included in this published article and its supplementary information files.