Embryonal Rhabdomyosarcoma Arising From the Buccal Mucosa in a Child: Imaging Findings

Significance Statement

In the pediatric age group, lesions in the head and neck region vary from infectious causes to malignancies. In the presence of a palpable mass that persists for more than 1 month and does not respond to antimicrobial therapy, further imaging should be performed. In this case report, we present a case of embryonal rhabdomyosarcoma (RMS) arising from the buccal mucosa in a child and emphasize radiological findings of this rare condition.

A 9-year-old male patient presented to the otolaryngology clinic with complaints of swelling and pain in his right cheek for 1 month. The patient had no known disease or history of trauma. Ultrasonography showed a hypoechoic solid lesion with lobulated contours adjacent to the right parotid gland in the right buccal region (Figure 1A). Contrast-enhanced computed tomography (CT) scan of the neck showed a mass lesion of 24 × 17 × 30 mm in the right buccal region. The lesion did not destroy adjacent bony structures and had heterogeneous enhancement (Figure 1B-D). Contrast-enhanced magnetic resonance imaging (MRI) performed to evaluate lesion margins showed a heterogenously enhancing lesion adjacent to the right parotid gland (Figure 2A, B, and D). Diffusion-weighted images showed significant diffusion restriction (Figure 2C). It was decided to perform an ultrasound-guided trucut biopsy due to suspicion of salivary gland malignancy. Pathologic analysis revealed a neoplastic formation consisting of primitive round cells and spindle cells invading the fibroconnective tissue and fat tissue. Immunohistochemical analysis revealed positivity for desmin, Myo D1, WT-1, TLE-1, and focal positivity for cyclin D1. Based on these findings, considering the patient’s age and the location of the lesion, the histological diagnosis was embryonal RMS.

Figure 1.

Ultrasound (A) shows a hypoechoic lesion (asterisks) in the right buccal region. Coronal (B) and axial (C) contrast-enhanced neck CT images showed a heterogeneously enhancing lesion (asterisks) in the right buccal region. Axial CT image with bone window settings (D) showed that the lesion (asterisks) did not destroy adjacent bones (arrows). CT, computed tomography.

Figure 2.

The right buccal mass (asterisks) is hypointense on the T1-weighted coronal section (A) and hyperintense on the T2-weighted fat-suppressed axial section (B). The mass restricts diffusion on the apparent diffusion coefficient map (C), suggesting hypercellular behavior (arrows). The post-contrast T1-weighted axial section (D) shows intense heterogeneous contrast enhancement.

RMS accounts for 7% of malignant tumors in children and is the most common soft tissue sarcoma in children. ¹ The onset of the disease is between 2 and 5 years of age. ¹ In adolescents over 12 years of age, a significant increase in morbidity has been observed. ¹ The incidence of RMS is approximately 1.5 times higher in boys than in girls. Approximately 40% of RMS cases are diagnosed in the head and neck region, with the face, eye, and nasal cavity considered the most frequently affected areas. ² RMS is particularly rare in the oral and perioral regions. ³ Symptoms and signs vary depending on the site of origin of the primary tumor, the age of the patient, and the presence or absence of metastases. RMS includes 3 histological subtypes: embryonal, alveolar, and pleomorphic. ⁴ The embryonal type is found most frequently in the head and neck. The first imaging method that should be performed in head/neck tumors is ultrasound. Contrast-enhanced MRI is considered the main radiological imaging in the diagnosis of head and/or neck RMS. It allows the precise determination and quantification of the tumor size, the assessment of local invasiveness, and the visualization of metastases to lymph nodes, meninges, and brain tissue infiltration. It is also used to assess residual tumor mass after surgery and to diagnose tumor recurrence. Contrast-enhanced CT is of great value in the evaluation of bone infiltration, especially in the facial cranium. Children with small, localized tumors with the appropriate histology and location show very high cure rates. However, even with aggressive multimodal therapy, less than 20% of patients with metastatic disease achieve long-term survival. ⁵