18F-fluorodeoxyglucose positron emission tomography-positive sarcoidosis after chemoradiotherapy for Hodgkin’s disease: a case report

INTRODUCTION The occurrence of granulomatous disease in the setting of Hodgkin's disease is rare; however, when it occurs it can pose significant clinical and diagnostic challenges for physicians treating these patients. CASE PRESENTATION We report the case of a 33-year-old Caucasian woman of Mediterranean descent with newly diagnosed 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography (PET)/computed tomography (CT) scan-positive, early-stage Hodgkin's disease involving the cervical nodes who, despite having an excellent clinical response to chemotherapy, had a persistent 18F-FDG PET scan-positive study, which was suggestive of residual or progressive disease. A subsequent biopsy of her post-chemotherapy PET-positive nodes demonstrated sarcoidosis with no evidence of Hodgkin's disease. CONCLUSION This case highlights the fact that abnormalities observed on posttherapy PET/CT scans in patients with Hodgkin's disease are not always due to residual or progressive disease. An association between Hodgkin's disease and/or its treatment with an increased incidence of granulomatous disease appears to exist. Certain patterns of 18F-FDG uptake observed on PET/CT scans may suggest other pathologies, such as granulomatous inflammation, and because of the significant differences in prognosis and management, clinicians should maintain a low threshold of confidence for basing their diagnosis on histopathological evaluations when PET/CT results appear to be incongruent with the patient's clinical response.