Role of ¹⁸F-FDG PET/CT in the Assessment of Kikuchi-Fujimoto Disease and Its Differential Diagnosis from non-Hodgkin Lymphoma

Objectives: Kikuchi-Fujimoto disease (KFD), also known as histiocytic necrotizing lymphadenitis, is a rare cause of lymphadenopathy with a highe prevalence in Asia. It can involve systemic lymph nodes, with cervical lymph nodes most commonly affected, and is easily misdiagnosed as lymphoma. This study investigated ¹⁸F-FDG PET/CT findings in KFD, and its usefulness for differential diagnosis from non-Hodgkin lymphoma (NHL).Methods: Three groups of patients [10 KFD, 12 indolent lymphoma (IL) and 15 aggressive lymphoma (AL)] underwent ¹⁸F-FDG PET/CT scan. Two experienced nuclear medicine physician independently interpreted the images and recorded the areas, size, and SUVmax and SULmax of lymph nodes involved. Possible organ involvements or other hypermetabolic lesions were also analyzed. Some serological indicators were collected.Results: The median age of KFD group was 23 (13-56) years old, with 8 women included. There were 9 cases with fever, 10 with lymph node enlargement, 3 with lymph node pain, 5 with skin rash, 5 with pharyngalgia, 3 with muscle pain, 5 with arthralgia and 1 with subcutaneous nodules of lower limbs. The course of disease was 31 (10-185) days. Leukocyte count was 8.4 (1.3-13.8)×10⁹/L, neutrophil count 5.2 (0.8-12.6)×10⁹/L, LDH 463.5 (188-1123) U/L, ESR 45 (4-101) mm/H, CRP 21.6 (11.5-101.8) mg/L, ALT 27 (11-273) U/L, AST 39.5 (21-276) U/L. At least two lymph node regions were involved in all participates, including neck in 10 cases, axilla in 9 cases, mediastinum in 8 cases, abdomen in 7 cases, pelvic in 6 cases and groin in 6 cases. The largest lymph node was 22 (13-36) mm, lymph node SUVmax 8.4 (6-19.2), highest SULmax 9.9 (4.9-15.2), liver SUVmax 2.8 (1.8-3.3), spleen size 9 (6-10) costal units, spleen SUVmax 3.4 (2.1-4.7), and bone marrow SUVmax 4.3 (3.1-5.4). High metabolic focis were found in 1 case of subcutaneous nodule with SUVmax 3.5, 2 cases of skin lesion with SUVmax 2.1 and 3.2, and 1 case of muscle lesion with SUVmax 2.1. The density of lymph nodes was uneven in 2 cases and blurred in 2 cases, which were confirmed by ultrasound. The correlation analysis showed that SUVmax of lymph nodes was correlated with LDH (r=-0.927, p<0.001), AST (r=-0.912, p<0.001) and ALT (r=-0.661, p=0.038). SULmax was correlated with LDH (r=-0.782, p=0.008) and AST (r=-0.754, p=0.012). The size of the largest lymph node was correlated with the course of disease (r=0.661, p=0.038).The highest SUVmax of lymph nodes in IL group and AL group were 5.9 (2-14.2) and 15.6 (5.9-31.3) respectively. The comparison among the three groups showed that there was a difference in highest SUVmax between the three groups (X²=14.5, p=0.001). There was no difference in highest SUVmax between KFD and IL group (p=0.093). However, the highest SUVmax of lymph nodes in KFD was significantly lower than that in AL (p=0.023). The highest SUVmax of lymph nodes in IL was significantly lower than that in AL (p<0.001). Conclusions: ¹⁸F-FDG PET/CT showed multiple hypermetabolic lymph nodes in KFD. The SUVmax of lymph nodes in KFD was significantly lower than that in AL, but there was no significant difference between KFD and IL. ¹⁸F-FDG PET/CT can be used to detect the area, number and metabolism of lymph nodes involved in KFD, and is helpful for differential diagnosis from NHL.