Case report The patient was referred to

Case report The patient was referred to the oral and maxillofacial department at the authors’ institution for further evaluation and treatment. The patient underwent tumor resection with left hemi-mandibulectomy with wide bony margins (Fig. 1A), and mandible reconstruction with fibula free flap and microvascular anastomosis (Fig. 1B). Postoperative follow up was uneventful with good positioning, healing and take of the graft. A postoperative radiograph of the resected specimen delineated the tumor extent in the mandible (Fig. 1C). Serial sections of the resected mandibular bone revealed a 3.5×1.8×1.5cm centrally located, irregular, gray–white, soft to rubbery mass. The tumor was focally infiltrating the cortex at the anterior medial part of the specimen but did not appear to infiltrate the periosteum (Fig. 1D). Histologically, the tumor revealed a densely cellular, undifferentiated sarcoma with a distinct biphasic pattern composed of prominent compact short fascicles of spindle beta lapachone that blended with nests of hyperchromatic round cells (Fig. 2A). The tumor cells displayed ill-defined borders, mild pleomorphism, a high nuclear/cytoplasmic ratio, fine granular chromatin, inconspicuous to small nucleoli and frequent mitoses. Cytoplasmic vacuolization and microcystic changes were focally present in the tumor. No tumor necrosis or pseudorosettes were present. Substantial amount of periodic acid-Schiff (PAS) positive, diastase labile cytoplasmic granules consistent with glycogen were present (Fig. 2B and C) in tumor cells. The tumor cells showed a strong membranous pattern of positivity for CD99 (Fig. 2D), vimentin and non-specific esterase (NSE) (not shown). A few scattered cells were positive for S100, neurofilament and synaptophysin (not shown). Cytokeratin (AE1/AE3, MAK6), leucocyte common antigen (LCA), myoglobin and myogenin stains were negative. CD117 stain was non-contributory. Based on tumor histomorphology and the immunohistochemical profile, a diagnosis of unusual variant of ES was favored. Tissue for genetic study was sent for confirmation of the histological diagnosis. Slides of resected tumor and the pathology report were sent to the outside institution that had interpreted the preoperative biopsy as ‘sarcoma not otherwise specified’. The diagnosis on the resection material was also ‘sarcoma not otherwise specified’ with a recommendation to carry out genetic studies. After tumor resection, the patient was transferred to another institution for chemotherapy, which sent slides out for independent consultation owing to ‘difficulty in classifying the tumor’. The results of the genetic test requested by the authors’ institution were positive for translocation rearrangement in EWR1 gene at 22q12 in 193 of 200 cells scored (97%) by fluorescence in situ hybridization (FISH) (Fig. 2E). The molecular study confirmed the authors’ diagnosis of ES. The pathology department of the treating institution was notified of the genetic test result. Their consulting institution repeated the genetic test and confirmed the diagnosis of ES, with a comment that ‘the tumor pattern was puzzling since it does not have features that are classic for the majority of ES/PNET’. Staging of the tumor in accordance with the American Joint Committee on Cancer (AJCC) Tumor Node Metastasis (TNM) system was T1 Nx Mx because the maximum diameter of the tumor in the mandible was 3.5cm. The patient started chemotherapy approximately 2 months after surgery. She received 12 cycles of chemotherapy, which consisted of vincristine, Adriamycin, and cyclophosphamide, at outside institution. Local radiation therapy was given due to a close margin (less than 1mm in the anteromedial aspect). She received 7000 cGy to the mandible region and 5000 cGy to the neck. On examination 2 months after surgery, the mandible was stable and she had adequate occlusion that was repeatable. The mucosa was intact with no lesions or breakdowns. She is currently approaching a 1 year (about 11 months) follow-up and is disease free.