Apparent Diffusion Coefficient on MRI and Pathological T Stage in Laryngeal Squamous Cell Carcinoma

Preoperative differentiation between pathological T3 (pT3) disease, representing locally advanced tumor confined to the larynx, and pathological T4 (pT4) disease, characterized by extension through the laryngeal cartilage and/or beyond the larynx, remains challenging in laryngeal squamous cell carcinoma (LSCC). This single-center retrospective study investigated the association between primary-tumor apparent diffusion coefficient (ADC) and pathological T stage and explored whether ADC could complement MRI-based morphological T classification. Twenty-eight patients with surgically confirmed, moderately differentiated LSCC were included (13 pT3 and 15 pT4). Mean ADC values were compared using the Mann-Whitney U test, and discrimination of pT4 disease was evaluated using receiver operating characteristic (ROC) analysis. Leave-one-out cross-validation was performed for internal validation of the ADC threshold and exploratory combined MRI-ADC rule. Mean ADC was significantly lower in pT4 than in pT3 tumors (760 ± 209 versus 1150 ± 188 × 10^-6 mm²/s; p < 0.001). ADC achieved an area under the ROC curve of 0.913 (95% confidence interval, 0.769-1.000). The apparent combined MRI-ADC rule yielded a sensitivity of 93.3%, specificity of 100%, and overall accuracy of 96.4%. Under leave-one-out cross-validation, the corresponding estimates were 93.3%, 92.3%, and 92.9%, respectively. No statistically significant association between primary-tumor ADC and pathological nodal status was detected. Primary-tumor ADC was associated with pathological T stage and showed potential complementary value to morphological MRI; however, the threshold and combined rule remain hypothesis-generating and require independent external validation.