Incidental dedifferentiated mediastinal liposarcoma on F-18-fluciclovine PET/CT.

Fat-containing mediastinal masses, particularly mediastinal liposarcomas, are rare neoplasms that can grow to large sizes before becoming symptomatic and may be incidentally found on radiology examinations. In this case report, a 67-year-old male with a history of prostate cancer status post prostatectomy presented for an F-18-fluciclovine PET/CT for a rising, clinically detectable PSA and indeterminate pelvic lymph nodes seen on multiparametric MRI of the prostate. No local tumor recurrence or metastatic disease from prostate cancer was identified, but the PET/CT demonstrated a mixed soft tissue and fat density prevascular (anterior) mediastinal mass with low-level radiotracer uptake. Following surgical consultation and resection, the final pathology revealed a dedifferentiated mediastinal liposarcoma. The case presented describes the appearance of an uncommon fat-containing mediastinal mass and describes several other fat-containing mediastinal masses that are important for radiologists to recognize in order to formulate accurate differential diagnoses and ensure appropriate further management for patients. Additionally, this case demonstrates that the radiotracer F-18-fluciclovine is not specific for prostate cancer, and its uptake can be seen with other entities such as in this case of sarcomatous malignancy.