Imaging Features and Clinical Characteristics of Granular Cell Tumors: A Single-Center Investigation

Background/Objectives: Granular cell tumors (GCTs) are rare neurogenic tumors with Schwann cell differentiation. Although most are benign, 1-2% exhibit malignant behavior. The imaging features of GCTs remain poorly characterized due to their rarity and anatomic variability. This study aims to elucidate the manifestations of GCTs in multimodal imaging across different anatomic locations. Methods: We retrospectively analyzed 66 histopathologically confirmed GCT cases (2011-2024), assessing their clinical presentations, pathological characteristics, and imaging findings from ultrasound (n = 31), CT (n = 14), MRI (n = 8), and endoscopy (n = 15). Two radiologists independently reviewed the imaging features (location, size, morphology, signal/density, and enhancement). Results: The cohort (mean age: 42 ± 12 years; 72.7% female) showed tendency in location towards soft tissue (48.4%), the digestive tract (30.3%), the respiratory system (7.6%), the breasts (7.6%), and the sellar region (6.1%). Six cases (9.1%) were malignant. The key imaging findings by modality were as follows: Ultrasound: Well-circumscribed hypoechoic masses in soft tissue (96.1%) and irregular margins in the breasts (80%, BI-RADS 4B) were found. MRI: The sellar GCTs exhibited T1-isointensity, variable T2-signals (with 50% showing "star-like crack signs"), and heterogeneous enhancements. The soft tissue GCTs were T1-hypointense (75%) with variable T2-signals. CT: Pulmonary/laryngeal GCTs appeared as well-defined hypodense masses with mild/moderate enhancements. Endoscopy: Submucosal/muscularis hypoechoic nodules with smooth surfaces were found. Malignant GCTs were larger (mean: 93 mm vs. 30 mm) but lacked pathognomonic imaging features. Three malignant cases demonstrated metastases. Conclusions: GCTs exhibit distinct imaging patterns based on their anatomical location. While certain features (e.g., star-like crack signs) are suggestive, imaging cannot reliably differentiate benign from malignant variants. Histopathological confirmation remains essential to diagnosis, particularly given the potential for malignant transformations (at 9.1% in our series). Multimodal imaging guides the localization and biopsy planning, but clinical-radiological-pathological correlation is crucial for the optimal management.