King Edward Memorial Hospital - Departments: Radiology

Radiology

Case of the Month

Case No. :	14
Month :	February
Year :	2000
Contributor :	Dr. Swati Ugale

Other Cases

Case Report | Differential Diagnosis | Diagnosis | Discussion

Case Report :

A 12 year old boy, presented with complaints of headache, nasal obstruction, rhinorrhoea and a tingling sensation in the nasopharynx of about two months duration. There was also a single episode of brisk epistaxis.

On examination, a polypoidal mass was seen to obstruct the conche and appeared to arise from the left lateral wall of the nasopharynx.

On CT Imaging (Figs 1-5) a mixed density, nonhomogenously enhancing soft tissue mass was seen to arise from the lateral wall and roof of the nasopharynx with infiltration into the adjacent soft palate. There was lateral extension of the lesion with effacement of pterygoid fat planes and infiltration of the medial pterygoid muscle. Posteriorly, encasement of carotid sheath near the base of the skull was noted. The lesion encircled the styloid process and extended upto the medial margins of the deep portion of the left parotid gland. The tumor encroached on the conchal orifices with resultant complete nasal obstruction.

There was erosion of the inferior margins of both pterygoid plates with tumor extension into the left pterygoid fossa. Axial bone windows showed erosion of the inferior margin of the left petrous apex. In addition, enhancement along the lateral aspect of clivus on the left side suggested tumor extension into the brain (extra-axial) probably, through the carotid canals along the course of the left ICA.

CT findings suggested a lateral nasopharyngeal neoplasm; the radiological features suggested malignancy.


Fig : 1.5

Fig : 2.5	Fig : 3.5

Fig : 4.5	Fig : 5.5

Differential Diagnosis :

A parapharyngeal abscess, which in children, can arise secondary to tonsillary infection & can extend from the skull base to the submandibular space. As this lesion can deviate the nasopharyngeal airway medially & the medial pterygoid laterally, it would be difficult to differentiate from neoplasm.

Nasopharyngeal angiofibroma - Though, a cursory review of the images might lead to a closer observation precludes the possibility with certainty. Angiofibromas in almost all cases arise near the pterygopalatine fossa with resultant widening of the fossa. In about half the cases, there is anterior bowing/destruction of the ipsilateral maxillary antrum. Post contrast CT images, in most of the cases, show intense enhancement. The age of presentation, the clinical features & the propensity to intracranial extension, are features shared in common with malignant tumors.

Hemangiomas are the most common tumors in the cervical region in children. They generally involve the oropharynx/ face & present as a sessile, reddish, submucosal mass near the base of the tongue. Phleboliths, if present, are diagnostic. On CT scan, these lesions show variable enhancement. The signal intensities on T1-W & T2-W images reflect the hemorrhagic content of the lesion.

Squamous cell carcinoma of the nasopharynx can develop in any age group but, is more commonly seen in middle aged & older persons. More than half the patients present with asymptomatic cervical node enlargement. Clinical features include otitis media [secondary to Eustachian tube involvement],nasal obstruction, epistaxis & trismus [secondary to infiltration of pterygoids]. They can also present with cranial neuropathies & the cavernous sinus syndrome.

Other entities less likely to be confused with the case described, are --

Lymphoma of the nasopharynx is usually of the NHL type & may involve any aspect of the Waldeyer's ring. They rarely involve the nasopharynx in isolation & can be confused with squamous cell carcinoma on imaging study. However their bulky appearance, an absence of necrosis & a lesser likelihood of regional infiltration help differentiate them from carcinomas.

Schwannomas are encapsulated benign tumors that most often develop in the 3^rd & 4^th decade of life. The most commonly affected nerves are the cervical spinal roots, the vagus & the sympathetic nerves. Located within the carotid sheath, they cause splaying of the carotid vessels & anterior displacement of the para pharyngeal space.

Neurofibromas are benign, non encapsulated, but, well-circumscribed tumors of the peripheral nerves. Solitary lesions are most commonly seen in the 3^rd decade. Unlike Schwannomas they rarely have cystic/necrotic components. A central hypointense focus, seen on T2-W MRI represents central fibrosis & is highly characteristic of these lesions.

Diagnosis :

A biopsy of the tumor revealed an "Embryonal rhabdomyosarcoma" .

Discussion :

There are three types of rhabdomyosarcoma :-

Embryonal Rhabdomyosarcoma : Occur mainly in first decade. However, a significant number of cases are seen in the second decade and in the adult life. Most arise in the head and neck and in urinary tract. They respond well to radio and chemotherapy. About a quarter of these cases metastasise to regional lymph nodes.

Alveolar Rhabdomyosarcoma :- Occur mainly in the ages between 15-25 years and mostly arise in the extremities and trunk, rather than in the head and neck.

Pleomorphic Rhabdomyosarcoma :- Occur in the 5^th and 6^th decades with a low incidence in the pediatric age group. In addition, they seldom occur in the head and neck.

The common sites of rhabdomyosarcoma in the head and neck are orbit (33%), nasopharynx (15%) and the middle ear/mastoid (15%). The less common locations are sinonasal cavities, the face, the neck and the larynx.

They commonly present with nasal obstruction, rhinorrhea, epistaxis, sinusitis, local pain, otolgia, headache, tooth ache, visual impairment and cranial nerve deficit. Regional lymph nodes and distant metastasis are seen in half the patients.

Intracranial extension through basal foramina may be seen with this tumor. The usual mode of invasion of foramen lacerum is through the carotid canal along the course of ICA, rather than by direct extension. Involvement of cavernous sinus is a grave prognostic sign.