Figure 1
Contrast enhanced axial CT scan of the parapharyngeal space
Slightly enhancing mass in the left parapharyngeal space. Peripheral demarcation of the mass is difficult to assess.
Clinical History
Pharyngeal pain and a left cervical swelling.
Swelling was seen to be pushing the soft palate towards the midline at endobuccal clinical examination.
Imaging Findings
The patient consulted for pharyngeal pain and a left cervical swelling.
This swelling was seen to be pushing the soft palate towards the midline at endobuccal clinical examination. CT scan and MRI were performed.
Discussion
Pleomorphic adenoma is the most common salivary gland tumor and represents about 80% of all benign tumors of the major salivary glands. 84% of them occur in the parotid gland, where 10% arise in the deep lobe. In about two-thirds of these deep lobe tumors the lesion is attached to the parotid gland only by a thin isthmus of tissue and develops in the parapharyngeal space. For the surgeon it is very important to know whether the mass originates in the parotid or in the parapharyngeal space, as this will determine the surgical approach. The tumor presents both on CT an MRI as a sharply delineated, round, oval or lobulated mass in the parapharyngeal space. On CT scan, the tumor is hypodense compared to surrounding parotid parenchyma, and does not enhance significantly on contrast enhanced studies. On MRI, signal intensity is intermediate on T1-weighted images. A mixture of intermediate and high intensity areas is seen on T2-weighted images, the latter corresponding to pockets of mucoid matrix. Study of the interface between the para-pharyngeal space tumor and the parotid gland is essential for revealing its origin. If a fat plane is seen on all axial images, the lesion is extra-parotid in origin. Although the soft tissue detail is better depicted on MR images, thin slices in the axial plane through the tumor should be obtained. In about 20% of cases, the tumor is in fact extra-parotid but it is so large that it obliterates the fat plane by compression or it originates from the gland capsule. In the very rare case of extraparotid tumor with parotid gland invasion, the differential diagnosis should include minor salivary gland tumors, neuromas and glomus tumors.
Differential Diagnosis List
Parotid pleomorphic adenoma
Final Diagnosis
Parotid pleomorphic adenoma
References
[1] Som PM, Bergeron TM. Head and neck imaging. In: Mosby-year book 1991, St Louis, Missouri, 1991; 321-325, 470-476.
[2] Som PM, Braun IF, Shapiro MD et al. Tumors of the parapharyngeal space and upper neck: MR imaging characteristics. Radiology 1987; 1645: 823-829. (PMID: 3039571)
[3] Som PM, Sacher M, Stollman Al et al. Common tumors of the parapharyngeal space: Refined imaging diagnosis. Radiology 1988; 169: 81-85. (PMID: 2843942)
Case information
| URL: | https://eurorad.org/case/924 |
| DOI: | 10.1594/EURORAD/CASE.924 |
| ISSN: | 1563-4086 |
Figure 2
Magnetic Resonance Imaging
Axial SE T1-weighted image: well-circumscribed lesion developing in the parapharyngeal space. Direct contact between a portion of the posterolateral marging and the parotid gland is seen. The mass pushes the masticator and carotid space, without infiltrating them.
Coronal Gadolinium-enhanced SE T1-weighted image shows pronounced enhancement all over the mass.
Axial SE T2-weighted image depicts the hyperintense aspect of the mass allowing detailed assessment of its borders. These characteristics were consistent with pleomorphic adenoma originating from the deep lobe of the parotid gland. The patient underwent surgery and histological analysis confirmed the diagnosis.
Contrast enhanced axial CT scan of the parapharyngeal space
Slightly enhancing mass in the left parapharyngeal space. Peripheral demarcation of the mass is difficult to assess.
Magnetic Resonance Imaging
Axial SE T1-weighted image: well-circumscribed lesion developing in the parapharyngeal space. Direct contact between a portion of the posterolateral marging and the parotid gland is seen. The mass pushes the masticator and carotid space, without infiltrating them.
Coronal Gadolinium-enhanced SE T1-weighted image shows pronounced enhancement all over the mass.
Axial SE T2-weighted image depicts the hyperintense aspect of the mass allowing detailed assessment of its borders. These characteristics were consistent with pleomorphic adenoma originating from the deep lobe of the parotid gland. The patient underwent surgery and histological analysis confirmed the diagnosis.