Dermatopathic Lymphadenitis A Pitfall for Lymphoma Evaluation by F-18 FDG PET/CT

Dermatopathic lymphadenitis (also known as lipomelanotic reticulosis, or Pautrier-Woringer disease) is a rare type of benign lymphatic hyperplasia associated with a variety of exfoliative or eczematoid type inflammatory erythrodermas. The axillary and inguinal regions are most commonly affected, although occasionally it can present in the head and neck as well. On histologic examination, the affected lymph nodes contain melanin and fat-laden reticular cells. This is a case of a 10-year-old boy with a history of severe eczema, who presented with enlarged lymph nodes. F-18 FDG PET/CT imaging showed intensely FDG-avid lymph nodes in the cervical, axillary, and inguinal regions and a diagnosis of lymphoma was suggested; however, histopathology revealed dermatopathic lymphadenitis. This entity is a potential pitfall in the F-18 FDG PET/CT evaluation of lymphoma and should be considered in the differential diagnosis, especially in individuals with a history of inflammatory erythrodermas. To our knowledge, this is the first report of F-18 FDG PET/CT imaging of dermatopathic lymphadenitis mimicking lymphoma.