CT of nasopharyngeal carcinoma: significance of widening of the preoccipital soft tissue on axial scans

Department of Diagnostic Radiology, National University Hospital, Singapore.

Axial CT scans of 60 patients with biopsy-proved nasopharyngeal carcinoma were reviewed with particular reference to sites of origin and routes of spread of disease. In all patients there was involvement of the pharyngeal space with blunting of the fossa of Rosenmuller and usually associated thickening of the adjacent levator veli palatini muscle. Tumor infiltration through the pharyngobasilar fascia manifested by obliteration or displacement of the parapharyngeal fat space was seen in 65% of the patients. T-staging by CT showed T1 (28%), T2 (20%), T3 (5%), and T4 (47%) involvement. In three patients there was bilateral symmetric blunting of the fossa of Rosenmuller with no evidence of tumor infiltration into the parapharyngeal space. The scans were initially interpreted as normal except for widening of the preoccipital soft-tissue area in the midline of more than 1.5 cm and up to 2.0 cm in the anteroposterior plane. Biopsy of the postnasal space was positive for tumor in these patients. With symmetric, early stage nasopharyngeal carcinoma, a confident radiologic diagnosis on CT can be difficult. If there is asymmetry of pharyngeal mucosal space or evidence of deep infiltration this should not be a problem. Although lymphoid adenoid tissue can sometimes result in widening of the preoccipital area, it is proposed that widening of this area of greater than 1.5 cm is an additional CT sign of nasopharyngeal carcinoma not previously emphasized. It is the result of early submucosal infiltration of the disease, and a patient with clinically suspected nasopharyngeal carcinoma should have aggressive deep biopsies of the fossa of Rosenmuller.
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