Presentation
Left cheek swelling showing gradual increase in size over 10 months.
Patient Data
Left masticator space shows an altered signal intensity heterogeneous expansile soft tissue mass, showing iso-intense signal intensity on T1W, heterogeneously hyperintense to intermediate signal intensity on T2W lesion with low signal striations, seen arising from the posterior body and ramus of the mandible. The lesion shows diffusion restriction and heterogeneous enhancement on post-contrast images.
The lesion extends from the anterior to the posterior border of the ramus of the mandible with thinning of the ramus of the mandible. The lesion is infiltrating the left masseter muscle laterally and medial pterygoid muscle medially. The left parotid gland is seen compressed along the inferolateral margin of the lesion and is medially displacing the left parapharyngeal space towards the midline without infiltrating it.
Ultrasound-guided core needle biopsy with needle tip within the lesion showing reverberation artifact.
Histopathology reports suggest a poorly differentiated malignancy.
Fluorescence in situ hybridization (FISH) is positive for EWSR1 (Ewing sarcoma breakpoint region 1) gene re-arrangement.
The immunohistochemistry (IHC) panel shows the tumor is positive for CK (moderately), NKX 2.2, and CD99, which are features of Ewing sarcoma.
Case Discussion
Ewing's sarcoma is a malignant tumor that mainly affects the long bones, almost half of the cases involve the femurs and pelvis.
Ewing's sarcoma is a rare aggressive variant of small round cell tumors and a rare cancer that usually occurs in childhood. It is the second most common malignant bone tumor occurring in children and young adults with a male predominance.
Ewing's sarcoma most commonly presents as a destructive, expanding mass with a laminated or onion skin periosteal reaction.
In patients with a soft tissue mass after 30 years, other small round cell tumors must be excluded, including large cell lymphoma and small cell carcinoma, before Ewing's sarcoma is diagnosed.