MRI Features of Head and Neck Adenoid Cystic Carcinoma: Differences Between Tubular/Cribriform and Solid Subtypes

<title>Abstract</title> <p> Purpose To evaluate MRI features of head and neck adenoid cystic carcinoma (ACC) according to predominant histologic subtype, with emphasis on differences between tubular/cribriform and solid groups. Methods This retrospective study included 45 patients with histopathologically confirmed head and neck ACC who underwent preoperative MRI. Predominant histologic subtypes were tubular ( <italic>n</italic>  = 4), cribriform ( <italic>n</italic>  = 33), and solid ( <italic>n</italic>  = 8). The tubular and cribriform subtypes were combined into a tubular/cribriform group and compared with the solid group. Results Myxoid components (56% vs. 0%), T1 hyperintensity (51% vs. 0%), and predominantly marked T2 hyperintensity of the solid component (35% vs. 0%) were more frequent in tubular/cribriform ACC than in solid ACC (all <italic>p</italic>  &lt; 0.05). The tubular/cribriform group also demonstrated higher T2 signal intensity ratios (SIRs) relative to the spinal cord (median, 1.35 [interquartile range (IQR), 1.06–1.68] vs. 0.91 [IQR, 0.72–1.12]) and higher apparent diffusion coefficient (ADC) values (median, 1.45 [IQR, 1.05–1.54] vs. 0.95 [IQR, 0.74–1.04] × 10⁻³ mm²/s) compared with the solid group (all <italic>p</italic>  &lt; 0.05). Tumors with higher T2 SIRs or ADC values were observed exclusively in the tubular/cribriform ACC group, whereas lower values were present in both groups. Conclusion Tubular/cribriform ACC was associated with myxoid components, T1-hyperintense areas, and predominantly marked T2 hyperintensity, as well as higher T2 SIRs and ADC values compared with solid ACC. In particular, higher T2 SIRs and ADC values may suggest tubular/cribriform ACC, whereas lower values alone are not specific for solid ACC. </p>