Ultrasonographic Differentiation Between Kikuchi's Disease and Lymphoma in Patients With Cervical Lymphadenopathy

Introduction Kikuchi's disease (KD) is a histiocytic necrotizing lymphadenitis that was described for the first time in Japan in 1972 almost simultaneously by Kikuchi and Fujimoto1-2. KD is a self-limited necrotizing lymphadenitis and occurs predominantly in females between 20 and 30 years old. Its main presentation is cervical lymphadenopathy. The diagnosis of KD is based on clinical manifestation, fine-needle aspiration cytology or excision biopsy. The pathological characteristics include patchy paracortical lymphohistiocytic aggregates with variable karyorrhexis and absence of granulocytic infiltration. Antibiotics are not helpful symptoms remit within six months spontaneously.

As KD is a benign and self-limiting disease, proper diagnosis may help avoid unnecessary treatment. KD can be easily confused clinically, pathologically, and radiologically with malignant lymphadenopathy, especially lymphoma. Several reports have described the CT characteristics of KD3-4, including enlarged, multiple lymph nodes that are homogeneously enhanced without evidence of gross necrosis. The CT appearance of Kikuchi's disease may be variable, thus mimicking lymphoma4. In previous work, the ultrasound appearance of KD has not been well-described and has been compared to lymphoma. In this study, we compared the sonographic characteristic of Kikuchi's disease and malignant lymphoma.

Patients and methods From November 2007 to September 2009, sonograms of twelve case notes with pathological diagnoses of Kikuchi's disease and twelve patients with malignant lymphoma were studied.

The sonograms were performed by the same sinologist (L-J Liao) using an ATL HDI 5000 with a high-resolution 7.5- to 12-MHz real-time linear-array transducer (Philips Ultrasound, Bothell, WA, USA). Morphological US parameters were thoroughly evaluated and recorded on the Marosis PACS system (Marotech Inc., Seoul, South Korea). The lengths of short and long axes of enlarged lymph nodes were measured and recorded. The shape of the lymph node was determined by the short axis to long axis ratio (S/L ratio). The nodal border was assessed for sharpness. Echogenicity of the lymph nodes was compared with that of adjacent muscles. Swelling of the surrounding tissues that presented with hyperechoic rims was assessed. The nodes were considered matted when a number of lymph nodes were clustered together. The internal architecture of lymph nodes was examined for the presence of heterogeneous micronodular pattern or reticulation.

Fisher's exact test and X 2 test were used to calculate the significance of the difference in gray-scale features. Mann-Whitney U tests were used to calculate the significance of the difference in nodal size and short- to long-axis ratio.