CASE 6041 Published on 10.10.2007

Rhabdomyosarcoma

Section

Head & neck imaging

Case Type

Clinical Cases

Authors

C.E Binns, D.R Salvage

Patient

49 years, male

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Clinical History

Facial pain and swelling.

Imaging Findings

This gentleman originally presented with facial pain which radiated to the left ear and was diagnosed with temporomandibular joint dysfunction. He returned to clinic 5 months later with worsening symptoms, dysphagia and 6 weeks of facial swelling. An MRI scan was performed with axial and coronal T1 images pre- and post- gadolinium, axial T2 SPAIR and coronal STIR. There is a huge lobulated mass centred on the left infra-temporal fossa extending from the skull base to the left tonsil. The mass crosses the midline, with extension to the right. It displaces the left parapharyngeal fat posterolaterally, fills the nasopharynx, indents the oropharynx and pushes the soft palate antero-inferiorly. The foramen ovale is expanded on the left side. Tumour passes through into the middle cranial fossa and elevates the temporal lobe. The tumour obliterates the left sphenoid sinus. It compresses and displaces the pterygoid and prevertebral muscles without obviously infiltrating them. The mass demonstrates a central non-enhancing area of necrosis or cystic change. No signs of lymphadenopathy are demonstrated. The patient had a biopsy of the mass which demonstrated a pleomorphic rhabdomyosarcoma. He was referred for consideration of chemoradiotherapy.

Discussion

Rhabdomyosarcoma is the commonest soft tissue sarcoma in the paediatric age group, with head and neck being the most frequent site of origin. 78% of cases occur before the age of 12. It is a rare diagnosis in the adult population. There are four main histopathological subtypes; embryonal, botryoid, alveolar and pleomorphic. Embryonal rhabdomyosarcoma occurs mainly in children and is the commonest type accounting for approximately 70-80% of tumours. The pleomorphic cell type is the least common overall but is the predominant form in adults and carries the worst prognosis. Metastatic spread occurs to the lungs, lymph nodes and bone marrow (then the heart and CNS). The prognosis is worse for tumours over 5cm in size and adults. Survival rates are also influenced by the histopathological subtype and tumour site. Multimodality treatment is used and has resulted in improved survival. A combination of chemotherapy, radiotherapy and surgical resection may be employed. The appearances on MRI are generally of a mass which is iso- or slightly hyperintense to muscle on T1 imaging and hyperintense to muscle and fat on T2 weighted images. The tumour generally shows marked enhancement with gadolinium. Most cases are homogenous in appearance, although heterogeneity and areas of necrosis or cystic change are described. There may be extensive bone destruction and intracranial extension via the skull base foramina often occurs. The infratemporal fossa is the nasopharyngeal portion of the masticator space. It lies between the pterygopalatine fossa medially and the zygoma laterally. A mass can be identified as being within this area when it is centred on the muscles of mastication and displaces the parapharyngeal fat posteriorly. The infratemporal fossa is a rare but recognised site for rhabdomyosarcoma. The imaging confirms the site and extent of the disease, biopsy and histology is required to make the diagnosis. MRI is the modality of choice both for initial assessment and follow-up to assess the outcome of treatment. The differential diagnosis for this mass included a nerve sheath tumour- a neurofibroma of the mandibular division of the trigeminal nerve would cause expansion of the foramen ovale. Large neurofibromas may undergo cystic degeneration. In this patient the rapid increase in size was suggestive of malignant degeneration.

Differential Diagnosis List

Rhabdomyosarcoma of the infratemporal fossa.

Final Diagnosis

Rhabdomyosarcoma of the infratemporal fossa.

References

[1] Prognostic factors in head and neck rhabdomyosarcoma.
Head Neck. 2002 May;24(5):468-73. Simon JH, Paulino AC, Smith RB, Buatti JM. (PMID: 12001077)

[2] A follow-up of rhabdomyosarcoma of the infratemporal fossa region in adults based on the magnetic resonance imaging findings: case reports.
Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 1998 Nov;86(5):616-25. Goto TK, Yoshiura K, Tanaka T, Kanda S, Ozeki S, Ohishi M, Kobayashi I, Matsuo K. (PMID: 9830658)

[3] Rhabdomyosarcoma of the head and neck in adults: MR and CT findings.
AJNR Am J Neuroradiol. 1996 Nov-Dec;17(10):1923-8. Lee JH, Lee MS, Lee BH, Choe DH, Do YS, Kim KH, Chin SY, Shim YS, Cho KJ. (PMID: 8933880)

[4] Rhabdomyosarcomas in the head and neck: MR imaging evaluation.
Radiology. 1990 Dec;177(3):683-6. Yousem DM, Lexa FJ, Bilaniuk LT, Zimmerman RI. (PMID: 2243968)

Case information

URL:	https://www.eurorad.org/case/6041
DOI:	10.1594/EURORAD/CASE.6041
ISSN:	1563-4086

Figure 1

MRI

Coronal T1 weighted image showing a lobulated, somewhat heterogenous mass which largely fills the left sphenoid sinus and the nasopharynx. The intrinsic signal of the mass is slightly higher than muscle.

Coronal STIR at the same position showing the high signal of the mass on this sequence.

T1 coronal post gadolinium image shows a moderate degree of enhancement of most of the mass but with a central area of necrosis/ cystic change.

T1 coronal image showing tumour extending through an enlarged left foramen ovale (arrow), there appears to be intact cortical bone on either side of the foramen suggestive of expansion rather than destruction. The tumour mass indents the deep suface of the left parotid.

Coronal STIR image shows the intracranial extension of the disease, slightly displacing the left cavernous sinus superiorly.

Coronal T1 post gadolinium. Enhancing tumour extends along the floor of the middle cranial fossa and elevates and distorts the temporal lobe.

T1 axial. The intermediate signal mass obliterates the left sphenoid sinus.

T1 axial image demonstrates the posterolateral displacement of the left parapharyngeal fat consistent with an infratemporal fossa mass (black arrow). There is compression of the left prevertebral muscles (white arrow). The grey arrow shows the normal right lateral pterygoid muscle, on the left this is either infiltrated or compressed to such an extent that it cannot be identified.

T2 axial image at the same level as 1h. The mass, which totally occludes the nasopharynx, is of intermediate T2 signal. Compare to the high signal of the fluid within the left petromastoid aircells (secondary to obstruction of the Eustachian tube) and mucosal thickening of the maxillary antra.