A 33-year-old man comes to the office due to 6 weeks of nonproductive cough and fatigue. The patient has also had subjective fevers and a 2.26-kg (5-lb) unintended weight loss over the same period. He has no prior medical conditions and takes no medications. The patient drinks alcohol socially and has a 6-pack-year history of smoking but quit 2 years ago. Vital signs are within normal limits. Lungs are clear on auscultation, and heart sounds are normal. Chest x-ray reveals clear lung fields but an enlarged mediastinum; subsequent CT scan of the chest shows hilar and mediastinal adenopathy. A positron emission tomography scan using 18-fluorodeoxyglucose demonstrates avid tracer uptake in the brain, kidneys, urinary bladder, and supraclavicular and mediastinal lymph nodes. Which of the following is the most likely diagnosis in this patient?
This young patient with hilar and mediastinal lymphadenopathy and B symptoms (eg, fevers, weight loss) likely has Hodgkin lymphoma, a lymphoid neoplasm with peak incidence in early adulthood and in those age >60. Most cases come to clinical attention due to painless lymphadenopathy in the cervical and/or supraclavicular chains or after chest radiograph shows a mediastinal mass. B symptoms are present in approximately 40% of cases.
The diagnosis is generally made by excisional lymph node biopsy; those with no clear evidence of peripheral lymphadenopathy on physical examination usually undergo imaging to identify a potential biopsy site. Positron emission tomography (PET) scan with 18-fluorodeoxyglucose (FDG), an analog of glucose, is often the imaging test of choice. Neoplastic cells (eg, supraclavicular and mediastinal lymph nodes in this patient) have a high metabolic rate and readily take up radiotracer on PET scan. However, radiotracer also pools in healthy organs with high glucose requirements such as the brain, kidneys, and liver; excretion of radiotracer also leads to enhancement throughout the urinary collecting system.
(Choice A) Glioblastoma multiforme would cause focal FDG uptake in the brain lesion and does not generally lead to cough or spread to the hilar or mediastinal lymph nodes.
(Choice C) Renal cell carcinoma usually metastasizes to the pulmonary parenchyma, which would be seen on PET scan.
(Choice D) Small cell lung cancer frequently spreads to the ipsilateral hilar and mediastinal lymph nodes; however, cases are rare in young adults, and a pulmonary mass is generally seen on imaging.
(Choice E) Transitional cell carcinoma would cause increased uptake of tracer in the urinary bladder, but abdominal lymphadenopathy would be seen rather than hilar or mediastinal lymphadenopathy.
Educational objective:
A positron emission tomography scan using a radiolabeled glucose analog can identify areas of enhanced metabolic activity (eg, cancer, infection). However, the tracer will also pool in healthy organs with high glucose requirements such as the brain, liver, and kidneys; uptake will also be seen in the urinary collecting system due to radiotracer excretion.