Lack of Increased FDG Uptake in the Lacrimal and Salivary Glands in Patients With Sarcoidosis and Potential Underlying Mechanism.

PURPOSE

Increased 67Ga uptake in the mediastinal/hilar lymph nodes ("lambda") and in the lacrimal/parotid/submandibular glands ("panda") often coexists in patients with sarcoidosis (Sarc-Pts). However, we observed that increased lacrimal/salivary uptake is uncommon on 18F-FDG PET/CT (FDG-panda) in many Sarc-Pts who showed increased mediastinal/hilar uptake (FDG-lambda). We evaluated parotid and lacrimal FDG activity in Sarc-Pts who showed FDG-lambda in comparison with a control patient group and attempted to find underlying mechanisms to explain the discrepancy between FDG and Ga uptake in these organs.

METHODS

Parotid FDG activity (FDG-P) was assessed visually using a 0- to 3-point scale (0 being = or minimally > background, and 3 > liver) and quantitatively using SUVmean in 52 confirmed Sarc-Pts with FDG-lambda (lambda group) as well as in 52 non-Sarc-Pts (control group). Lacrimal FDG activity (FDG-L) was assessed visually (0 being = or minimally > subcutaneous tissue, and 1 clearly > subcutaneous tissue).

RESULTS

There was no significant difference in the parotid SUVmean between lambda (1.88 ± 0.65) and control (1.76 ± 0.62) groups (P = 0.333). Also, there was no difference in visually graded FDG-P between the 2 groups (P = 0.257). None of the patients in all groups showed apparently abnormal (grade 1) FDG-L.

CONCLUSIONS

Increased FDG-L/FDG-P is rare in Sarc-Pts demonstrating FDG-lambda, which is strikingly different from the clinical experience as well as the reported data on Ga scintigraphy. Discrepancy in various cytokine levels between lacrimal samples and intrathoracic lesions in Sarc-Pts reported in the literature appears to correlate well with variable Ga and FDG uptake in the lacrimal gland and intrathoracic lesions.