Sikandar Mohd Shaikh DMRD, Presenter: Nothing to Disclose

To review F-18 FDG PET/CT findings of Sarcoidosis mimicking malignancy

F-18 FDG PET/CT scans in which Sarcoidosis was misinterpreted as malignancy were included. Sarcoidosis was confirmed by biopsy or surgery. F-18 FDG PET/CT finding was retrospectively evaluated. The maximum standardized uptake value (SUVmax) of the primary tumors and TB mimicking malignancy were measured.

50 cancer patients (11 for initial staging and 14 for restaging) and 14 Sarcoidosis patients without any malignancy were included (M:F=17:13, age 45±13). Sarcoidosis involved lung (n=17), cervical (n=10), mediastinal (n=5) and abdominal (n=5) nodes, bowel (n=1), adrenal gland (n=1) and pleura (n=1) in the 32 patients. Sarcoidosis caused false positive reading in 9 cases out of 11 staging cases leading to overstaging, 12 out of 14 restaging cases, and 7 patients without any malignancy, 4 falsely considered to have lung cancer and 3 abdominal malignancy. TB involved contralateral supraclavicular node (SCN) in 5 of 7 patients with breast cancer and right SCN in 4 of 7 patients with abdominal malignancy. In staging PET/CT, the mean SUVmax of the primary tumor was 5.0±3.6 (2~11.4), while that of Sarcoidosis considered as metastasis was 4.5±2.4 (2.0~6.5) in lung and 5.6±3.3 (2.4~8.9) in lymph node. In restaging PET/CT, the SUVmax of TB considered as recurrence was 2.8±0.8 (2.2~4.3) in lung and 4.8±2.3 (2.2~8.0) in lymph node. The mean SUVmax of Sarcoidosis mimicking malignancy was 3.7±1.3 (range 2.2~4.7) in lung and 6.1±3.3 (3.4~9.7) in abdomen.

Sarcoidosis mimicked primary cancer, metastasis or recurrence on FGD PET/CT, and led to upstaging in majority of cancer patients. SUV was not useful in discrimination. When FDG uptake is seen in contralateral SCN in breast cancer patients, and right SCN in abdominal malignancy patients, Sarcoidosis should be considered as differential diagnosis

PET-CT HAS MANY MIMICKS IN RELATION TO NEOPLASTIC LESIONS WHICH ARE SOMETIMES  VERY DIFFICULT TO DIFFERENTIATE.

Shaikh, S, Role of F-18 FDG PET/CT in Differentiating Findings of Sarcoidosis versus Malignancy.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14013129.html