Pebbled mosaic‐like heterogeneous echogenicity in ovarian immature teratomas and correlation of ultrasound patterns with pathological grades

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.