Imaging of unicentric hyaline-vascular variant of Castleman disease: Emphasis on perilesional fat stranding and fatty proliferation.

The hyaline-vascular variant of Castleman disease (HVCD) is relatively uncommon and demonstrates no specific clinical or laboratory findings; therefore, its preoperative diagnosis warrants a radiological evaluation. This study aimed to review imaging findings of HVCD, focusing on perilesional fat stranding and fatty proliferation. Patients with a pathologically confirmed HVCD diagnosis who had undergone CT were recruited from five hospitals from January 2000 to March 2023. Three experienced radiologists assessed CT findings, including lesion location, lesion size, calcification, enhanced pattern, feeding vessel visualization, and arterial enhancement. Perilesional fat stranding, fatty proliferation, neighboring fascial thickening, and surrounding lymphadenopathy were the primary targets of analysis. Moreover, the intensities and apparent diffusion coefficient (ADC) values on MRI and the maximum standardized uptake value (SUVmax) on ¹⁸F-fluorodeoxyglucose positron emission tomography (PET) were evaluated. This study enrolled 43 patients (mean age 41.3 years ± 14.6 [standard deviation], 23 women). All lesions were well-defined round masses. Calcification and feeding vessels were detected in 21% (9/43) and 86% (36/43) of the patients, respectively. Perilesional fat stranding and fatty proliferation were observed in 44% (19/43) and 19% (8/43), respectively, with fatty proliferation detected only in retroperitoneal HVCD. Neighboring fascial thickening and surrounding lymphadenopathy were identified in 21% and 60%, respectively. The mean ADC value and SUVmax were 0.884 × 10^-3 mm²/s and 5.0, respectively. Retroperitoneal HVCD cases with perilesional fatty proliferation demonstrated a higher visceral fat ratio than those without (p = 0.046). Perilesional fat stranding and fatty proliferation were new characteristics of HVCD, especially in retroperitoneal cases.