Case of the Month—July 2003

Head and Neck Cancer—Detection of Unknown Primary Cancer

History
A 52-year-old male presented with palpable mass in left cervical region. An enlarged left cervical node was identified by CT. Biopsy of lymph node confirmed squamous cell cancer. Initial staging by conventional imaging and ENT exam failed to detect the primary cancer site. The patient then underwent left neck node dissection.

A PET study was ordered to evaluate the primary site of the cancer.

Finding of PET
The PET study demonstrated a focus of increased FDG uptake at the left base of the tongue, identified as likely primary cancer.

Follow-up
Biopsy of the left tongue base confirmed squamous cell cancer.


Sagittal projection along with anterior view reveal focus of increased FDG uptake at left base of the tongue (see arrows).

How Did PET Help?
PET was able to identify the primary cancer, which had not been detected by conventional imaging studies. The results of the PET study changed the radiation therapy treatment plan, reducing the radiation field and avoiding unnecessary extra radiation damage to the patient.

Discussion
For patients with an unknown primary head and neck tumor, despite extensive clinical exam and extensive anatomic imaging procedures, PET helps to detect the primary in about 25% of these patients.1 PET is also very useful in the detection of residual/recurrent cancer after radiation therapy and cervical node dissection. PET can also be used to monitor therapy response.

1. Johansen, J., Eigted, A., Buchwald, C., Theilgaard, S., and Hansen, H.S., (2002) Laryngoscope, 112(11) 2009-14.

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