PSMA Uptake Due to Recent Intra-articular Injection.

Area of Science:

• Nuclear Medicine
• Oncology
• Radiology

Background:

• Prostate adenocarcinoma staging commonly utilizes imaging techniques like 99mTc-PSMA and 99mTc-MDP bone scans.
• Interpreting these scans requires careful consideration of potential confounding factors that may mimic metastatic disease.

Purpose of the Study:

• To report a case of atypical 99mTc-PSMA uptake in the knee.
• To emphasize the importance of differentiating non-malignant findings from metastatic lesions in prostate cancer staging.

Main Methods:

• Whole-body 99mTc-PSMA (technetium-99m-labeled prostate-specific membrane antigen) and 99mTc-MDP (technetium-99m-labeled methylene diphosphonate) scans were performed for staging.
• 99mTc-PSMA SPECT/CT (single-photon emission computed tomography/computed tomography) was used for detailed imaging of the affected area.

Main Results:

• Whole-body PSMA scan showed increased tracer uptake in the right knee and periarticular space.
• SPECT/CT revealed arthritis with effusion in the right knee's periarticular region.
• The patient had received an intra-articular corticosteroid injection two days prior to the scan.

Conclusions:

• Atypical 99mTc-PSMA uptake patterns can occur and may be mistaken for metastatic disease.
• Awareness of recent interventions, such as intra-articular injections, is vital for accurate interpretation of PSMA scans.
• Differentiating inflammatory or iatrogenic uptake from metastasis improves diagnostic precision in prostate cancer management.