Inguinal kimura disease misdiagnosed as Castleman disease: A case report and analysis of ultrasonographic features

Kimura disease (KD) is a rare chronic inflammatory proliferative disorder. Inguinal involvement is particularly uncommon, and its clinical and imaging appearances may mimic lymphoproliferative disease. We report a 38-year-old man (body mass index, 29.4 kg/m²) with a pruritic right inguinal mass present for more than 5 years. A previous diagnosis of Castleman disease (CD) had led to chemotherapy and surgery without satisfactory control. Ultrasonography showed a 70 × 32 × 46 mm heterogeneous hypoechoic subcutaneous mass containing scattered internal cord-like hyperechoic bands. Color Doppler imaging demonstrated abundant central arborizing intralesional vascularity. The absolute peripheral blood eosinophil count was 3.77 × 10⁹/L (32.6%). Noncontrast computed tomography demonstrated the dominant right inguinal mass and additional nodal lesions. Histopathologic examination after complete excision showed lymphoid follicular hyperplasia, extensive interfollicular eosinophilic infiltration, and eosinophilic microabscesses, confirming KD. This case expands the sonographic spectrum of inguinal KD and suggests that the combination of marked eosinophilia, internal cord-like hyperechoic bands, and central arborizing vascularity may help distinguish KD from CD before surgery.