Herpes Simplex Necrotic Lymphadenitis Masquerading as Richter's Transformation in Treatment-Naive Patients With Chronic Lymphocytic Leukemia.

Richter's transformation from chronic lymphocytic leukemia (CLL) to aggressive lymphoma is a relatively rare event with well-characterised clinical and radiological features, and can typically be distinguished from infectious complications of CLL. Opportunistic infections in CLL happen predominantly in the context of immunosuppressive therapy and/or relapsed/refractory disease. Herpes simplex viral (HSV) lymphadenitis is a rare phenomenon in treatment-naive CLL patients with only six cases reported in the English-language literature. Its diagnosis is challenging; its management and the outcome of the subsequent treatment for CLL are not well documented. We report three cases of rapidly progressive lymphadenopathy occurring in the context of previously untreated CLL, clinically and radiologically mimicking Richter's transformation, but histologically confirmed as necrotic HSV lymphadenitis. We describe the presentation, diagnosis and management of all three cases, including for the first time the positron emission tomography-computed tomography (PET-CT) appearance of this condition, as well as how we later on delivered CLL-directed immunochemotherapy safely and successfully without recrudescence of HSV-related disease. Our cases underscore the importance of obtaining biopsy in all cases of rapidly progressive or disconcordant lymphadenopathy in CLL patients, or in those with highly FDG-avid adenopathy on PET-CT.