martedì 18 settembre 2007

Nasopharyngeal carcinoma


Figure 1: Axial CT image displayed at bone window reveals the destructive lesion at the skull base involving the basi-sphenoid, basi-occiput, pterygoid plates and extending across the midline.
Figure 2: Axial T2-WI reveals soft tissue mass in the right lateral pharyngeal recess of the nasopharynx, involving the right veli palatine muscle and effacement of the Fossa of Rosenmüller.
Figure 3: Axial T2 WI reveals the mass to extend superiorly involving the right pterygopalatine fossa and the right pterygoid recess. The right masticator space appears spared.
Figure 4: Axial T2 WI reveals the mass to extend to involve the right sphenoid sinus and petrous apex, and into the right cavernous sinus, encasing and narrowing the right cavernous carotid artery.
Figure 5: Axial contrast-enhanced T1-weighted image obtained at level of nasopharynx shows fullness and enhancement in region of right Rosenmüller's fossa.
Figure 6 and Figure 7: Axial contrast-enhanced T1-weighted images reveal extension into the sphenoid sinus, petrous apex, pterygopalatine fossa and right cavernous sinus.
Figure 8: Coronal contrast-enhanced T1-weighted MR image reveals invasion of nasopharyngeal cancer into right cavernous sinus with encasement of internal carotid artery.
Figure 9: Coronal contrast enhanced T1-weighted image reveals an enhancing mass in sphenoid sinus region and increased enhancement (compared with normal left side) extending through the right foramen ovale.

Diagnosis: Nasopharyngeal carcinoma

Most nasopharyngeal malignancies in adults are carcinomas, usually of the squamous cell variety (80%). Squamous cell carcinomas (SCC) of the nasopharynx are relatively rare in the United States and much more common in Asia, being endemic in Southern China. A strong correlation between Epstein-Barr virus and nasopharyngeal cancer is well documented. Genetic predisposition and association with consumption of salted fish and preserved foods is also suspected.

Nasopharyngeal squamous cell cancer usually presents before age 50 and is more common in males (M:F=2.5:1). It usually presents late because of its infiltrative pattern. The most common presentation is an asymptomatic neck mass due to metastatic adenopathy. Serous otitis media may result from eustachian tube dysfunction resulting in otalgia and unilateral conductive hearing loss. Nasal obstruction and epistaxis are other common symptoms. Perineural spread and intracranial extension can cause headaches and cranial nerve deficits.

Nasopharyngeal cancers usually present as a poorly marginated nasopharyngeal mucosal space mass with deep extension and invasion. They tend to grow along the path of least resistance: along submucosal and soft tissue planes, along neurovascular bundles and intracranially through neural foramina at the skull base. Nodal metastases are present in 90% of cases at presentation. Distant metastases to the bones, lung or liver are seen in less than 10% of cases.

These tumors show squamous differentiation with intracellular bridges or keratinization. There are three main histologic subtypes- keratinizing, non-keratinizing and undifferentiated carcinoma.

Biopsy is the way to establish the diagnosis since imaging cannot distinguish among nasopharyngeal malignancies. Imaging plays a crucial role for mapping out the spread of tumor and planning radiation therapy/ surgical resection. Enhanced MR imaging is the best tool for evaluating intracranial extension via direct, perineural or perivascular routes. Thin section CT helps to evaluate bone invasion. CECT is preferred for evaluation of cervical metastatic nodes, except retropharyngeal adenopathy which is better seen on MRI. These tumors are strongly FDG avid.

XRT is the mainstay of treatment with combined XRT and chemotherapy used for advanced disease.

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