Objective:

To report a case of synchronous bilateral phyllodes tumors and highlight the diagnostic challenges associated with 18F-FDG PET-CT imaging, particularly in distinguishing between reactive and metastatic processes.

Key Findings:

• The left breast mass was diagnosed as a borderline phyllodes tumor, while the right was benign, highlighting the variability in tumor behavior.
• All axillary lymph nodes showed reactive hyperplasia with no evidence of metastasis, underscoring the importance of accurate interpretation of imaging.
• Marked axillary FDG avidity may indicate reactive inflammation rather than true metastasis, which is critical for surgical decision-making.

Interpretation:

The case illustrates the potential for misinterpretation of 18F-FDG PET-CT results in the context of phyllodes tumors, emphasizing the need for careful clinicopathologic correlation to avoid misdiagnosis.

Limitations:

• Synchronous bilateral phyllodes tumors are rare, limiting generalizability of findings.
• The role of 18F-FDG PET-CT in phyllodes tumors is not well established, and further research is needed to clarify its utility.

Conclusion:

Complete surgical excision with negative margins is crucial in managing phyllodes tumors, and axillary surgery should be approached with caution due to the risk of misinterpreting reactive lymphadenopathy as metastasis, highlighting the need for thorough evaluation.