Features of Hypermetabolic Hilar and Mediastinal Lymph Nodes on 18F-FDG PET
| Entity | Clinical features | CT features |
| Sarcoidlike reaction | History of prior malignancy; entity may occur at time of initial cancer diagnosis to years later, often with no clinical evidence of disease | No pulmonary changes; patient classically shows bilateral mild to moderately enlarged hilar and mediastinal lymph nodes; enlarged or hypermetabolic lymph nodes may be present elsewhere |
| Sarcoid | Bias toward young and middle-aged African–American women; clinical complaints often include erythema nodosum, uveitis, and acute polyarthritis, with nonspecific respiratory symptoms, fatigue, weight loss, and fever | Pulmonary findings may often be absent though when present show nodular pattern along lymphovascular bundles; patient classically has bilateral lobulated, mild to moderately enlarged hilar and mediastinal lymph nodes; lymph nodes may have peripheral thin egg-shell calcifications |
| Pneumoconiosis | History of occupational exposure such as surface mining; patient may be asymptomatic early on and then develop shortness of breath and respiratory symptoms along with pulmonary changes | Diffuse reticular or nodular/reticulonodular pattern of pulmonary disease; lung findings can coalesce into massive pulmonary fibrosis; lymph nodes often have egg-shell calcifications |
| Infection | No age or sex predilection; signs and symptoms of respiratory infection are present (i.e., fever, productive cough, leukocytosis, and elevated C-reactive protein) | Pulmonary features of infection (bronchopulmonary nodules, infiltrate, or consolidation); lymph nodes ipsilateral to pulmonary abnormality are typically at upper limit of normal size to mildly enlarged |
| Radiation-induced inflammation | History of prior malignancy with treatment by radiotherapy; patient may be asymptomatic or have dyspnea or nonproductive cough | Sharply marginated, localized fibrotic area of lung; lymph nodes ipsilateral to fibrosis are normal to mildly enlarged |
| Lymphoma | Age predilection based on type of lymphoma; patient may present with weight loss, night sweats, fever, decreased appetite | Rarely has pulmonary findings; marked nodal enlargement is often bilateral though may be asymmetric; conglomerate nodal masses may be present |
| Bronchogenic carcinoma | Older individuals, often with history of smoking or pulmonary fibrosis, present with weight loss, decreased appetite, hemoptysis | Lung mass or nodule; nodal enlargement is typically ipsilateral to lesion |
| Metastases | History of malignancy, possibly with increasing tumor markers suggestive of disease recurrence; is most commonly seen in tumors with predilection for mediastinal or hilar metastases (i.e., esophageal cancer or head and neck cancer) | Lymph nodes often asymmetric or unilateral; evidence of metastases may be present in lungs, bones, or elsewhere |