[Granulation tissue: pitfall in therapy control with F-18-FDG PET after chemotherapy]

Area of Science:

• Oncology
• Nuclear Medicine
• Immunology

Background:

• False positive findings in positron emission tomography (PET) scans using fluorodeoxyglucose (FDG) are often attributed to uptake in inflammatory foci.
• Assessing treatment response in Non-Hodgkin lymphoma (NHL) using FDG-PET requires differentiating tumor activity from inflammatory changes.

Observation:

• A 53-year-old patient with abdominal NHL underwent FDG-PET post-chemotherapy to evaluate persistent tumor vitality.
• The scan revealed increased FDG uptake at the margin of a residual mass.
• Histological examination showed a necrotic center surrounded by granulation tissue.

Findings:

• Activated neutrophils and macrophages can exhibit increased FDG uptake, mimicking residual tumor.
• This heightened uptake in inflammatory cells must be considered during chemotherapy treatment monitoring.

Implications:

• FDG-PET interpretation in lymphoma patients undergoing chemotherapy needs to account for inflammatory responses.
• Accurate assessment of treatment efficacy relies on distinguishing true tumor metabolism from FDG uptake by activated immune cells.