PET positive generalized lymphadenopathy and splenomegaly following interferon-alfa-2b adjuvant therapy for melanoma

Interferon-alfa (IFN-alpha) is used in patients with various inflammatory and neoplastic disorders. We recently encountered fluorodeoxyglucose (FDG) uptake in generalized lymphadenopathy, splenomegaly, and the marrow in a patient receiving high dose interferon-alpha-2b (IFN-alpha) as adjuvant therapy for the treatment of malignant melanoma. Biopsy of an enlarged hypermetabolic axillary lymph node revealed only a reactive node. Discontinuation of IFN-alpha caused regression of splenomegaly and lymphadenopathy within 3 months.A marrow "hyperstimulation" pattern that can include the spleen is a well-recognized phenomenon on (fluorodeoxyglucose) FDG positron emission tomography/computed tomography (PET/CT) scans in patients receiving chemotherapeutic agents like interferon, though classically due to colony stimulating factors, but does not generally include lymphadenopathy. This case, which likely reflects an interferon-induced pseudolymphoma, highlights the importance of a drug history and clinical correlation for the proper interpretation of FDG PET/CT scans.