Chien Shih a, b, Jenq-Yuh Ko a, Cheng-Ping Wang a, b, Lai-Lei Ting c, Jong-Kai Hsiao d
aDepartment of Otolaryngology, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan
bDepartment of Otolaryngology, National Taiwan University Hospital, Yun-Lin Branch, Yun-Lin, Taiwan
cDivision of Radiation Oncology, Department of Oncology, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan
dDepartment of Medical Imaging, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan
Abstract
Positron emission tomography (PET) is valuable for detecting locoregional recurrences of nasopharyngeal carcinoma (NPC) with a high sensitivity and fair specificity. A negative PET result is generally thought to confidently exclude the presence of a tumor. However, a false-negative PET scan is more dangerous than false-positive results because an undiscovered recurrent tumor may eventually lead to the patient's death without proper treatment. In this report, we describe a false-negative PET scan in a NPC patient with a recurrent tumor in the left cavernous sinus, presenting as a new onset of left 6th cranial nerve palsy 1 year after irradiation. The first magnetic resonance imaging (MRI) and PET scan failed to disclose any abnormalities. The second MRI performed 3 months after the first scans demonstrated a new abnormal lesion in the left cavernous sinus, which had resolved in the following MRI after re-irradiation. Therefore, clinical observation with suggestive symptoms is still important, even with negative imaging results. Close follow-up with a series of imaging studies must be performed when indicated.
Keywords
Cavernous sinus; Diplopia; Magnetic resonance imaging; Nasopharyngeal carcinoma; Positron emission tomography
