MR Imaging Criteria for the Detection of Nasopharyngeal Carcinoma: Discrimination of Early-Stage Primary Tumors from Benign Hyperplasia

Abstract

Background and purpose: MR imaging can detect nasopharyngeal carcinoma that is hidden from endoscopic view, but for accurate detection carcinoma confined within the nasopharynx (stage T1) must be distinguished from benign hyperplasia of the nasopharynx. This study aimed to document the MR imaging features of stage T1 nasopharyngeal carcinoma and to attempt to identify features distinguishing it from benign hyperplasia.

Materials and methods: MR images of 189 patients with nasopharyngeal carcinoma confined to the nasopharynx and those of 144 patients with benign hyperplasia were reviewed and compared in this retrospective study. The center, volume, size asymmetry (maximum percentage difference in area between the right and left nasopharyngeal halves), signal intensity asymmetry, deep mucosal white line (greater contrast enhancement along the deep tumor margin), and absence/distortion of the adenoidal septa were evaluated. Differences were assessed with logistic regression and the χ² test.

Results: The nasopharyngeal carcinoma center was lateral, central, or diffuse in 134/189 (70.9%), 25/189 (13.2%), and 30/189 (15.9%) cases, respectively. Nasopharyngeal carcinomas involving the walls showed that a deep mucosal white line was present in 180/183 (98.4%), with a focal loss of this line in 153/180 (85%) cases. Adenoidal septa were absent or distorted in 111/111 (100%) nasopharyngeal carcinomas involving the adenoid. Compared with benign hyperplasia, nasopharyngeal carcinoma had a significantly greater volume, size asymmetry, signal asymmetry, focal loss of the deep mucosal white line, and absence/distortion of the adenoidal septa (P < .001). Although size asymmetry was the most accurate criterion (89.5%) for nasopharyngeal carcinoma detection, use of this parameter alone would have missed 11.9% of early-stage T1 nasopharyngeal carcinomas.

Conclusions: MR imaging features can help distinguish stage T1 nasopharyngeal carcinoma from benign hyperplasia in most cases.

Fig 1.

A, Axial T1-weighted postcontrast MR image of the nasopharynx in a 51-year-old man with NPC (open arrow). An asymmetric tumor with a lateral center at the level of the left pharyngeal recess is confined to 1 side of the nasopharynx. The tumor exhibits homogeneous low contrast enhancement with an intact deep mucosal white line (small solid arrows) along the deep margin. B, Axial T1-weighted postcontrast MR image of the nasopharynx in a 68-year-old man with NPC (open arrow). An asymmetric tumor with a lateral center at the level of the left pharyngeal recess is confined to 1 side of the nasopharynx. The tumor exhibits homogeneous moderate contrast enhancement with a focal loss of the deep mucosal white line (small solid arrows) along the deep margin. C, Axial T1-weighted postcontrast MR image of the nasopharynx in a 44-year-old woman with NPC (open arrow). An asymmetric tumor with a lateral center at the level of the right side of the roof shows heterogeneous contrast enhancement.

Fig 2.

Axial T1-weighted postcontrast MR image of the nasopharynx in a 32-year-old woman with NPC (open arrow). An asymmetric tumor with a central center in the adenoid exhibits homogeneous contrast enhancement and loss of the normal adenoidal septa.

Fig 3.

A, Axial T1-weighted postcontrast MR image of the nasopharynx in a 51-year-old man with NPC (open arrows). A symmetric tumor with diffuse involvement of all nasopharyngeal walls exhibits homogeneous contrast enhancement without a white line along the deep mucosal margin. B, Axial T1-weighted postcontrast MR image of the nasopharynx in a 59-year-old man with NPC (open arrows). A symmetric tumor with diffuse involvement of the nasopharyngeal walls exhibits homogeneous low contrast enhancement and an intact mucosal white line along the deep margin. The adenoid extends along the posterior wall from the roof, with an adenoidal “stripe” on the right (curved open arrow) but not on the left side. A small right retropharyngeal node is also indicated (solid arrow). The patient had bulky N3-stage metastatic nodes below this level.

Fig 4.

A, Axial T1-weighted postcontrast MR image of the nasopharynx in a 53-year-old man with BH1 (open arrows). An area of diffuse symmetric mucosal thickening with homogeneous contrast enhancement is visible. B, Axial T1-weighted postcontrast MR image of the nasopharynx in a 28-year-old man with BH2 of the adenoid (open arrow). The symmetric lesion exhibits contrast-enhancing septa that run perpendicular to the nasopharyngeal wall and are separated by columns of low contrast enhancement. C, Axial T1-weighted postcontrast MR image of the nasopharynx in a 48-year-old woman with BH2 along the nasopharyngeal walls (open arrows). An area of diffuse, symmetric homogeneous low contrast enhancement and an intact deep mucosal white line along the deep margin are visible.

Fig 5.

A, Boxplots showing differences in the T1 postcontrast signal intensity ratios (relative to muscle) among NPC, BH1, and BH2. B, Boxplots show differences in the T2 signal intensity ratios (relative to muscle) among NPC, BH1, and BH2.

Fig 6.

Receiver operating characteristic curve of the percentage difference in area for NPC detection.

Fig 7.

Axial T1-weighted postcontrast MR image of the nasopharynx in a 52-year-old man with asymmetric BH. Greater thickening is observed in the left side of the roof (open arrows), where a focal area of mucosal thickening comprises a superficial band of low contrast enhancement overlying an intact deep mucosal white line (BH type 2). A Tornwaldt cyst is also present (solid arrow).