73 yrs old male presented with painless left neck mass. A contrast enhanced CT of the neck showed necrotic left level II cervical lymphadenopathy concerning for metastatic disease, and a 1.7 x 1.5 cm mass arising from the superficial lobe of the right parotid gland. A 1.2 cm nodule was also visualized in the right lung apex. FNA of the enlarged cervical lymph node showed metastatic keratinizing squamous cell carcinoma.

Whole body FDG-PET CT showed asymmetric uptake in the left tonsil with a maximum SUV of 8.6. Hypermetabolic left cervical level II lymphadenopathy had a maximum SUV of 6.9. Indeterminate focal hypermetabolism was seen in the right parotid gland with a maximum SUV of 6.0. The right upper lobe pulmonary nodule also showed hypermetabolism (SUV 3.9) suspicious for neoplastic involvement.

Biopsy of the left tonsil showed squamous cell carcinoma and the biopsy of right parotid gland showed pleomorphic adenoma, a benign tumor.

The right upper lobe pulmonary nodule was biopsied and showed non small cell carcinoma with features of adenocarcinoma.

Thus, PET-CT localized the primary squamous cell carcinoma to left tonsil and diagnosed an incidental second primary malignancy in the lung

1. FDG PET and PET/CT for the detection of the primary tumour in patients with cervical non-squamous cell carcinoma metastasis of an unknown primary. Paul SA, Stoeckli SJ, von Schulthess GK, Goerres GW. Eur Arch Otorhinolaryngol. 2007 Feb;264(2):189-95.

2. The presentation of malignant tumours and pre-malignant lesions incidentally found on PET-CT. Even-Sapir E, Lerman H, Gutman M, Lievshitz G, Zuriel L, Polliack A, Inbar M, Metser U. Eur J Nucl Med Mol Imaging. 2006 May;33(5):541-52.

This case was compiled by Dr. Scott Lenobel, BCM