Clinical
Presentation: A
62-year-old male in need of further evaluation after suspicious imaging findings.
Imaging Findings: There is a diffuse, but extensive, soft tissue mass that involves the bilateral sphenoid, ethmoid (mainly right side), right maxillary and right frontal sinuses. The mass does not show intracranial extension. No apparent involvement of the orbits is seen.
In addition, large bilateral lymphadenopathy can be visualized. The great vessels on the right side of the neck are encircled and compressed by the lymphadenopathy, especially the right internal jugular vein.
Figure 1: Axial T1 MR revealing lymphadenopathy.
Figure 2: Axial T1 MR with soft tissue mass.
Figure 3: Coronal T1 MR with mainly right-sided mass lesion.
Figure 4: Axial face CT with soft tissue masses.
Figure 5: Axial MR and PET allowing well-defined tumor location.
Diagnosis:Rhabdomyosarcoma
Discussion:Rhabdomyosarcomas are malignant soft tissue tumors of skeletal muscle progenitor cells. They are the most common soft tissue tumor in children. With approximately 350 new cases diagnosed each year, they account for about 3% of childhood malignancies.
Between 30 and 40% of rhabdomyosarcomas arise in the head and neck. Other common sites include the genitourinary tract and reproductive organs (20-25%), the extremities (20%) and the trunk (7%). Within the head and neck, about half occur in parameningeal sites, while 25% occur in the orbits, and the final 25% occur in other locations, including the scalp, parotid gland, and neck.
Rhabdomyosarcomas are classified into several subtypes, the two largest of which are embryonal RMS and alveolar RMS. Embryonal rhabdomyosarcoma is the most common subtype. It is usually found in the head, neck, or genitourinary tract of children under the age of 15, and is considered to be the most treatable of the subtypes. Alveolar rhabdomyosarcoma is more common in the extremities of older children and teenagers, and is typically more aggressive than embryonal RMS. The subtypes are associated with varying etiology, location, histologic findings, and prognosis.
Clinical presentation of rhabdomyosarcoma in the head and neck varies with location. Parameningeal RMS commonly presents as nasal/sinus obstruction or otitis media. Orbital tumors may present with proptosis, dysconjugate gaze, and poor vision. Tumors in other locations in the head and neck usually present as enlarging, painless masses.
CT imaging of head and neck rhabdomyosarcoma typically demonstrates homogeneous soft tissue masses isointense to surrounding muscle. As a result, the tumor margins are often poorly defined. CT images are useful for inspecting for damage to adjacent bone structures. MR imaging is generally more accurate for determining the margins of the tumor. On T2-weighted images, the tumor mass typically appears hyperintense to muscle and fat.
Treatment includes surgery, radiation therapy, and chemotherapy. Surgery is often a challenge with head and neck RMS because of the risk of damage to nearby structures. The prognosis for patients with rhabdomyosarcoma depends on a number of factors, including tumor location, subtype, stage, and treatment. For children with head and neck RMS, the 5 and 10 year survival rates are 69% and 65% respectively. Common long-term complications affect stature, cosmetic appearance, and dentition.
References:
Lee JH, Lee MS, Lee BH, Choe DH, Do YS, Kim KH, Chin SY, Shim YS, Cho KJ. Rhabdomyosarcoma of the head and neck in adults: MR and CT findings. AJNR Am J Neuroradiol. 1996 Nov-Dec;17(10):1923-8. [Medline]
Raney RB, Asmar L, Vassilopoulou-Sellin R, Klein MJ, Donaldson SS, Green J, Heyn R, Wharam M, Glicksman AS, Gehan EA, Anderson J, Maurer HM. Late complications of therapy in 213 children with localized, nonorbital soft-tissue sarcoma of the head and neck: A descriptive report from the Intergroup Rhabdomyosarcoma Studies (IRS)-II and - III. IRS Group of the Children's Cancer Group and the Pediatric Oncology Group. Med Pediatr Oncol. 1999 Oct;33(4):362-71. [Medline]
Harnsberger HR: Diagnostic Imaging: Head and Neck, 1st ed., Elsevier, 2004.
