A novel contrast-enhanced CT classification system for differentiating signet ring cell carcinoma in gastric cancer ovarian metastases: a pathologically correlated study

Background To identify contrast-enhanced computed tomography (CECT) features for distinguishing signet ring cell carcinoma (SRCC) from non-SRCC in gastric cancer ovarian metastasis (GCOM), to develop a diagnostic nomogram using generalized estimating equations (GEE), and to explore the value of these features in predicting primary gastric pathology and primary-metastatic pathological concordance. Methods This retrospective study enrolled 137 female patients with pathologically confirmed GCOM. Two abdominal radiologists independently analyzed preoperative CECT features. Tumors were first classified as cystic-dominant, mixed cystic-solid, or solid-dominant based on imaging morphology. A novel classification system based on solid component enhancement was defined: type I (weak enhancement, ΔHU<40HU), type II (strong homogeneous enhancement, ΔHU≥40HU), or type III (heterogeneous enhancement). “Critical regions” were defined as hypodense areas (20-30HU on non-contrast) showing minimal enhancement (10-20HU increase post-contrast). Univariable and multivariable GEE with an exchangeable correlation structure were used to account for within-patient clustering and to construct a diagnostic nomogram. Model performance was assessed using receiver operating characteristic (ROC) curve analysis with 1,000 cluster bootstrap resamples. Results Three independent predictors for GCOM-SRCC differentiation were identified: lesion size, solid type, and critical region. The nomogram achieved an AUC of 0.802 (95% CI: 0.743–0.872), with an optimism-corrected AUC of 0.795. Secondary exploratory analyses showed limited discriminatory value in predicting primary gastric pathology (AUC = 0.651–0.667) and pathological concordance (AUC = 0.674–0.702), likely reflecting underlying tumor biologic heterogeneity. Conclusions The proposed CECT-based nomogram provides a non-invasive exploratory tool for preoperatively estimating the probability of SRCC in GCOM. However, prospective multicenter validation is required before its clinical utility can be established.