口腔悪性リンパ腫の鑑別診断におけるapparent diffusion coefficientの有用性

Malignant lymphoma (ML), a lymphocyte-derived malignancy, is classified into Hodgkin lymphoma and non-Hodgkin lymphoma (NHL). In the oral cavity, NHL is the predominant type. However, diagnosing oral ML is challenging owing to its clinical similarity to other lesions. Diffusion-weighted magnetic resonance imaging and apparent diffusion coefficient (ADC) values may aid in differential diagnosis. Therefore, in the present study, we aimed to evaluate the usefulness of ADC in distinguishing ML from squamous cell carcinoma (SCC) and salivary gland carcinoma (SGC).

This retrospective study included 11 patients with ML, 35 with SCC, and 19 with SGC treated at our institution between 2012 and 2022. Clinical data and ADC values were analyzed, and magnetic resonance imaging was performed using a 3.0 T scanner.

Clinical assessment alone frequently resulted in misclassification of ML cases, with most cases initially suspected of having benign or other malignant tumors. ML demonstrated markedly lower ADC values (mean 0.67 ± 0.13 × 10⁻³ mm²/s; range 0.45-0.87) than SCC (1.21 ± 0.14) and SGC (1.30 ± 0.27) (both P < 0.0001), with minimal overlap between the groups. An ADC cutoff of 0.87 × 10⁻³ mm²/s identified ML with 100% sensitivity and 98.2% specificity (area under the curve: 0.99), indicating a strong diagnostic differentiation from carcinoma cases.

ADC assessment may facilitate early suspicion of oral ML and help clinicians in prioritizing it within the differential diagnosis. Integrating ADC values into the diagnostic workflow could facilitate early recognition and more appropriate biopsy strategies, thus supporting timely management.