Preoperative lymphocyte-to-monocyte ratio and CT-measured appendix diameter in occult appendiceal neoplasms: a matched case–control analysis

Occult appendiceal tumors may present as acute appendicitis, hindering preoperative recognition. Existing clinical and imaging criteria remain nonspecific. This study aimed to identify practical preoperative predictors by integrating hematologic indices with CT morphometry in a matched case–control design. In this retrospective matched case–control study, 2,599 adult appendectomy cases (2020–2024) were screened. Sixty-two had histologically confirmed neoplasms; after excluding incomplete records, 40 malignant cases were matched 1:4 by age and sex with 160 benign controls. Preoperative lymphocyte-to-monocyte ratio (LMR) and CT-measured appendix diameter were analyzed using conditional logistic regression. After matching (SMD < 0.01), malignant cases showed higher LMR (3.41 ± 1.89 vs. 2.51 ± 1.31, p = 0.001) and larger diameter (12.6 ± 4.1 mm vs. 10.8 ± 2.7 mm, p = 0.001). LMR > 3.8 increased malignancy risk 3.77-fold, diameter > 14 mm increased it 4.9-fold, and both combined raised risk nearly 18-fold (AUC = 0.74; Hosmer–Lemeshow p = 0.09). Elevated LMR and enlarged appendix diameter independently predict occult appendiceal neoplasms. Patients exceeding both thresholds may benefit from intraoperative frozen-section or extended resection. Multicenter validation is warranted.