A 13-year-old boy referred to the Department of Oral and Maxillofacial Surgery from the Pediatric Department due to a 4-day history of asymptomatic swelling in the right cheek.
No other symptoms were reported or loss of consciousness occurred.
Physical examination revealed a solid elliptical mass between the body of malar bone and the anterosuperior part of the right maxillary bone.
There was a boundary between the lesion and the surrounding muscle and not the skin.
Intraoral examination revealed a firm, mobile, painless mass in the gingiva at the bottom of the vestibule of the right upper arch.
No other findings were found in the head and neck examination.
A biopsy with intraoral access was performed.
Histologically, the mass was constituted mostly by a compact proliferation of small cells.
The greatest increase was observed in the presence of nuclei and uniforms, which revealed granular chromatin with peripheral condensation, as well as low and slightly eosinophilic cytoplasm.
The stroma was scarce with occasional fibrous tissue tracts.
Median immunohistochemical analysis was positive for CD-99.
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Magnetic resonance imaging (MRI) revealed a well-defined, encapsulated solid tumor measuring approximately 24 × 13 mm anterior to the right maxillary sinus, with anterior displacement of the zygomatic muscles.
The lesion was not located in neighboring structures and showed intense enhancement with gadolinium after its administration, suggesting high cellularity of the lesion.
No underlying bone alterations or significant adenoid growth were identified.
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Prior to treatment, distant metastases were ruled out by biopsy and aspiration of bone marrow, in addition to performing a whole-body PET-CT.
Treatment for ESS was administered following the Euro-EWING 99 protocol.
The control MRI showed the disappearance of the lesion, although with persistence of a thickening that compromised the facial muscles (lower face of the orbicularis oculi and elevator of the upper lip).
After this, we proceeded to the surgical treatment of the remaining lesion, performing extensive resection of the facial muscles and blaming tissue affected.
It was deepened to the plane of maxillary bone, without resection for not observing clinically or radiographically tumorless.
The patient was discharged on the second postoperative day with good general condition and no postoperative complications.
Histological analysis of the surgical specimen revealed absence of malignant cells and negative margins.
Follow-up MRI findings were described as post-surgical changes in the baseline study, without criteria for rest or underlying tumor recurrence.
