Proliferation PET/CT Imaging of Salivary Gland Tumor

Abstract

Salivary gland tumors are rare neoplasms which vary in terms of origin and malignant potential. 2-[18F]-fluoro-2-deoxy-d-glucose (FDG)-positron emission tomography (PET) has limited ability to differentiate between different types of salivary gland tumors because both Warthin's tumors and pleomorphic adenomas usually show increased FDG uptake, with no statistically significant difference in standardized uptake value (SUV) compared with malignant salivary gland tumors. Here, we discuss 4'-[methyl-11C]-thiothymidine (4DST) PET, which provides cell proliferation imaging capable of demonstrating intense uptake in parotid carcinoma and Warthin's tumor, but no uptake in parotid pleomorphic adenoma. This is the first report of the potential of proliferation PET/ computed tomography (CT) imaging for characterizing salivary gland tumors based on the molecular pathogenesis of the tumor.

Keywords: 4DST PET/CT; FDG PET/CT; Warthin’s tumor; cell proliferation imaging; pleomorphic adenoma; salivary gland tumor.

Figure 1

A man in his 80s with carcinoma arising in the left parotid gland. (A) Fused FDG-PET/CT image (axial view), (B) fused 4DST PET/CT image (axial view), and (C) gadolinium (Gd)-enhanced MRI (axial view). Gd-enhanced MRI shows homogeneous enhancement of an irregular-shaped lesion in the left parotid gland. High FDG uptake (SUV_max: 21.8) as well as lower, but unequivocal, 4DST uptake (SUV_max: 6.0) were confirmed in the lesion.

Figure 2

A man in his 60s with pathologically proven Warthin’s tumor in the parotid glands bilaterally. (A) Fused FDG-PET/CT image (axial view), (B) fused 4DST PET/CT image (axial view), and (C) plain CT (axial view). Intense uptake of both FDG (SUV_max: 9.6) and 4DST PET/CT (SUV_max: 12.0) is seen in bilateral nodular lesions, which show high intensity on plain CT (arrows) consistent with the typical features of Warthin’s tumors. Aspiration biopsy revealed oncocytes and abundant lymph-node cells and epithelium with eosinophilic cytoplasm, and a diagnosis of Warthin’s tumor was made based on pathological findings.

Figure 3

A woman in her 70s with a tumor of the right parotid gland, highly suspected to be pleomorphic adenoma (arrows). (A) Fused FDG-PET/CT image (axial view), (B) fused 4DST PET/CT image (axial view), (C) Gd-enhanced MRI (axial view), and (D) T2WI MRI image (axial view). On T2WI, a well-circumscribed intraparotid mass of intermediate-to-high signal and a low-signal rim is seen, with heterogeneous nodular enhancement, characteristic of pleomorphic adenoma [20]. The tumor shows increased FDG uptake (SUV_max: 5.2) but no 4DST uptake.