Rhabdomyosarcomas (head and neck)

Rhabdomyosarcomas of the head and neck represent a large proportion (~40%) of all rhabdomyosarcomas and are the most common soft tissue sarcomas of the head and neck. For a general discussion of this tumor, please refer to rhabdomyosarcoma.

Pathology

There are usually of the embryonal in cell subtype and are essentially only seen in children. They are classified by location into:

• orbital rhabdomyosarcoma: good prognosis (90% long term survival)
• para-meningeal rhabdomyosarcoma: worse prognosis (50% long term survival)
• other head and neck locations

Middle ear rhabdomyosarcomas are rare, accounting for only 7% of head and neck rhabdomyosarcomas. They typically present similarly to chronic otomastoiditis and are usually diagnosed too late for curative treatment. Frequently (30%) cranial nerve involvement is present at the time of diagnosis.

Microscopic appearance

Histologically, rhabdomyosarcomas are low-grade small round blue cell tumors. Ewing sarcoma, neuroblastoma, and lymphoma share similar characteristics that make histopathologic differentiation of rhabdomyosarcoma hard.

Radiographic features

Ultrasound

Rhabdomyosarcomas resemble neuroblastomas in echotexture and often demonstrate low to medium echogenicity. With color Doppler, there is often variable internal vascularity.

MRI

• T1: isointense to slightly hyperintense
• T2: hyperintense
• T1 C+: marked contrast enhancement
• +/- intralesional hemorrhage or necrosis
• +/- diffusion restriction 

Radiology report

As the differential diagnosis is vast, and the imaging findings are non-specific, it would be useful to describe in detail the:

• location
• involvement of adjacent compartments
• perineural, vascular, and osseous involvement
• presence of lymphadenopathy

Treatment and prognosis

Treatment depends on the location and disease extent, with orbital and non-parameningeal head and neck locations having a better prognosis. Chemotherapy is first line for the treatment of rhabdomyosarcomas, with radiation therapy and surgery utilized for local tumor control.

Differential diagnosis

The differential diagnosis for more superficial non-parameningeal locations includes:

• chondrosarcoma
• fibrosarcoma
• synovial sarcoma

The differential diagnosis for deeper parameningeal locations includes:

• hemangioendothelioma
• nasopharyngeal carcinoma
• osteosarcoma, and primitive neuroectodermal tumor

The sonographic differential also includes:

• fibrosarcoma
• malignant fibrous histiocytoma
• angiosarcoma
• neurofibrosarcoma