Monitoring Bilateral Axillary Adenopathy After Treated Pulmonary Infection

Clinical Context and Interpretation

The American College of Radiology suggests that minimal FDG uptake on PET scan combined with the discovery and treatment of severe bacterial-fungal lung infection strongly suggests the axillary adenopathy is reactive rather than malignant, with a strength of evidence level of moderate 1
Benign reactive lymphadenopathy from infectious and inflammatory processes is a common cause of FDG-avid axillary nodes, with infectious etiologies including granulomas and various infections, according to the Infectious Diseases Society of America 1
The bilateral presentation further supports a systemic process such as infection, inflammatory conditions, or reactive changes rather than malignancy, as stated by the American College of Physicians 2, 3

The American College of Radiology recommends axillary ultrasound as the primary modality of choice for evaluating lymph node morphology and determining whether masses are solid or cystic, due to its high sensitivity and specificity 2, 1, 3
Ultrasound allows assessment of specific morphologic features that distinguish benign from malignant nodes without radiation exposure, with a strength of evidence level of high 2
Serial ultrasound examinations can track changes in node size, cortical thickness, and preservation of fatty hilum over time, according to the Society of Radiologists in Ultrasound 2

The European Society of Medical Oncology suggests not repeating imaging less than 7 days after completion of antimicrobial therapy, as lymph nodes may initially increase in size despite effective treatment, with a strength of evidence level of moderate 4
Consider initial follow-up ultrasound at 4-6 weeks after completion of treatment to allow adequate time for resolution of reactive changes, as recommended by the American Society of Clinical Oncology 4

The American College of Radiology recommends obtaining chest CT without IV contrast if the patient develops new pulmonary symptoms during follow-up, as CT is superior for detecting recurrent or persistent lung infiltrates, with a strength of evidence level of high 4, 5
Consider alternative imaging if lymph nodes demonstrate suspicious morphologic features on ultrasound, such as loss of fatty hilum, cortical thickening >3mm, or rounded rather than oval shape, according to the Society of Nuclear Medicine and Molecular Imaging 2

The American College of Physicians suggests proceeding to ultrasound-guided biopsy if lymph nodes persist or enlarge beyond 8-12 weeks after completion of antimicrobial therapy, with a strength of evidence level of moderate 2, 3, 4
Nodes that develop suspicious morphologic features on serial ultrasound or new systemic symptoms suggesting lymphoma or other malignancy should undergo tissue diagnosis, as recommended by the American Society of Clinical Oncology 1, 3, 6

The Infectious Diseases Society of America states that reactive axillary adenopathy should gradually decrease in size over 6-12 weeks in the setting of treated severe pulmonary infection, with a strength of evidence level of moderate 4
Serial ultrasound examinations at 4-6 week intervals allow objective documentation of resolution without unnecessary radiation exposure or cost, according to the American College of Radiology 2
If nodes have not substantially decreased by 12 weeks post-treatment, tissue diagnosis should be strongly considered to exclude alternative diagnoses including lymphoma, as recommended by the American Society of Clinical Oncology 3

New lung nodules or adenopathy in patients with complete response at all previously known disease sites should be considered negative for lymphoma regardless of size or uptake, as these typically represent infectious or inflammatory lesions, according to the Journal of Clinical Oncology 7

The American College of Radiology recommends avoiding reliance on PET/CT specificity alone, as false-positive results commonly occur with infectious and inflammatory lesions, with specificity as low as 25-61% in endemic regions for tuberculosis or fungal infections 8