Fig. 2

a T2-weighted STIR image of the neck (transaxial) showing bilateral level 2 lymph nodes in patient with KFD. b Fused FDG PET and T2-weighted STIR image (transaxial) showing FDG avid bilateral level 2 nodal lesions. c Fused FDG PET MR (coronal) image of the head, neck, and thorax showing “string of pearls sign.” The arrows depict the array of FDG avid lymph nodal lesions on both sides of neck and thorax (cervical, supraclavicular, axillary, and deep pectoral stations). d Biopsy sections from the left axillary lymph node show partly preserved architecture with reactive follicles in the cortex. Intervention seen in the sheets of histiocytes along with admixed necrotic areas with nuclear debris. The cells have moderate pale/vacuolated cytoplasm, round to oval nuclei with open chromatin, and small prominent nucleoli. Few cells appear crescentic. No evidence of malignancy. Lymph node biopsy indicates necrotizing lymphadenitis from KFD due to the histiocytic cellular infiltrate along with phagocytic debris and crescent nuclei. e MR brain transaxial image shows diffuse enhancement and thickening of pachymeninges (arrows), suggestive of meningitis. f Fused PETMR brain transaxial image (arrows) depicts sites of abnormal increased FDG uptake corresponding to MR detected meningeal enhancements (pachymeningitis)