Primary Ewing’s sarcoma/primitive neuroectodermal tumor of the ileum: case report of a 16-year-old Chinese female and literature review

A 16-year-old Chinese girl presented complaining of anemia and interval hematochezia. Her hemoglobin was 54 g/L on admission. Capsule endoscopy and double-balloon enteroscopy showed mucosal hyperemia, edema and mass protrusion on the ileal wall. Computed tomography (CT) scans and three-dimensional reconstruction revealed a 10.0 × 7.3 × 5.3 cm irregular mass that had developed from the ileal wall in the right lower quadrant (Fig. 1a-h). The lesion showed intense but inhomogeneous enhancement following contrast administration (Fig. 1e-h), particularly in the arterial phase. There was a small amount of effusion in the pelvic cavity. Pelvic magnetic resonance imaging (MRI) indicated a right ovarian cyst in addition to the above mass. Both CT and MRI prompted suspicion of malignant GIST of the small bowel. Her serum CA-125 was slightly increased (50.5 U/mL, standard 0–36 U/mL), but the other markers were within normal limits. The tumor and a loop of small intestine were resected through a right ventral midline incision. The patient recovered uneventfully. Postoperative bone scintigraphy proved that there was no lesion in the skeletal system (Fig. 1 d). Her chest CT scan and cerebral MRI were also unremarkable. Thus, the patient was classified as T2aN0M0 according to the 8th edition of the AJCC Cancer Staging Manual.

On laparotomy, a large cystic and solid mass 10.5 cm in diameter was found arising from the ileal wall. The cut tumor surface showed large central hemorrhagic and necrotic changes and pseudocystic degeneration. The tumor tissue was mostly light gray and solid, with some softer and more friable reddish congested areas (Fig. 2).

Cross sections revealed solid nests of small round tumor cells arising from the muscular layer and infiltrating all layers of the ileum wall. Cystic and hemorrhagic changes were seen on part of the sections, as were sharply demarcated borders that were frequently covered by intact serosa. No vascular tumor embolus or perineuronal invasion were observed. The serosal layer and the surgical margins of the specimen were free of disease. Under high-power view, tumor cells were round or elliptical, possessing scant eosinophilic cytoplasm and abortive pseudorosette formation. The tumor cell nuclei were round, with exquisite chromatin, ambiguous nucleoli, and 9/10 high-power-field pathological mitoses (Fig. 3a-c). Tumor cells showed positive immunoreactivity for Vimentin and CD99 (Fig. 3 d, j) and moderate staining for Cam5.2, Syn and PR (Fig. 3 f, g, k). Results were negative for CKpan, LCA, S-100, HMB45, Melan-A, CD31, CD34, NSE, P53, CD56, CgA, SMA, Desmin, CD117, Dog-1, ER, Bcl-2, and alpha-inhibin.

Dual color break-apart probe FISH examination showed that 90% of the cells (100 counted cells per slide) exhibited 1 yellow and 1 red signal (1F1R) and that 6% of the cells exhibited 1 yellow, 1 red and 1 green (break-apart) signal (1F1G1R). However, only 4% cell had two yellow signals, which proved a break of the EWSR1 locus (2 F) (Fig. 4a-c).

Transmission electron microscopy revealed dense clusters of tumor cells, interspersed with a few interstitial cells (Fig. 5 a). The tumor cells were small and irregular, with scant cytoplasm and organelles, and significant nuclear atypia (Fig. 5 a). Some cells had small nucleoli (Fig. 5 a). Occasionally, gap junctions between the cells were observed (Fig. 5 b), but neuroendocrine granules in the cytoplasm were rarely seen (Fig. 5 c). Most cells had glycogen particles attached to the endoplasmic reticulum (Fig. 5 d).

The patient underwent an exploratory laparotomy, and tumor resection was performed along with 60 cm of ileum. The patient refused chemotherapy and/or radiotherapy as adjuvant treatments. She is currently alive (10 months after the surgery) without any signs of recurrence.