Introduction

Ewing’s sarcoma (ES) is the second most frequent primary malignant bone tumor in the pediatric age group, with an estimated incidence of 2.9:100,000. ES represents 34% of primary bone tumors¹,². The axial skeleton, pelvis, femur, and ribs are the most common locations. The most frequently reported site of metastasis is the lungs. In children, ES is more frequent in males, with a ratio of 3:2 and a mean age of 14 years¹,³. ES is a very aggressive cancer, with a survival rate of 70% to 80% for patients with localized, usual-risk disease and 30% for those with metastatic disease¹, representing 20-30% of cases. ES originates from mesenchymal cells. Therefore, 15% of ES are extraosseous as they arise from different tissues. Here, we describe an unusual case of intestinal ES in a pediatric patient.

Clinical case

We describe the case of a 14-year-old male with no relevant history. The patient presented with an anemic syndrome, unintentional weight loss of 6 kg, and diaphoresis of 8 weeks of evolution. The attending physician requested a complete blood count that revealed non-regenerative anemia, with hemoglobin (Hb) 5.3 g/dl. Subsequently, the patient was referred to the National Institute of Pediatrics.

Initial physical examination showed pallor, systolic murmur III-IV, splenomegaly, and pain in the left abdomen. Among the initial studies, abdominal ultrasonography (USG) showed a mass of 115 x 102 x 80 mm with hypodense areas on the left flank, and computed tomography (CT) showed evidence of a peritoneum-dependent tumor without abdominal lymphadenopathy. PET/CT with FDG (fluorodeoxyglucose positron emission tomography/CT) showed an 11.2 x 10.5 x 7.2 cm tumor in the left flank, extending longitudinally from the lower splenic border to the upper third of the proximal insertion of the ipsilateral psoas muscle and transversely from the anterior abdominal wall to the anterior border of the left kidney with no infiltrations. A USG-guided biopsy of the abdominal mass was performed, showing monotonous cells with round nuclei, inconspicuous nucleolus, and scant eosinophilic cytoplasm arranged in solid clusters intermixed with areas of tumor necrosis (Figure 1). Immunohistochemical staining with CD99 and Fli-1 was positive (Figure 2); CD-117, myeloperoxidase (MPO), Wilms tumor (WT-1), CD34, and extranodal spread (ENS) markers were negative. Due to these histological and immunohistochemical findings, Ewing’s sarcoma was diagnosed.

Figure 1 A: histological section showing the transition zone between the preserved intestinal wall and the tumor (H&E 5x). B: small monotonous cells with round nuclei and little eosinophilic cytoplasm (H&E 40x). 

Figure 2 A: positive CD99 on the tumor cell membrane. B: nuclear positive FLI-1 in tumor cells. 

Complete surgical resection was performed (Figure 3), and chemotherapy treatment with vincristine/doxorubicin/cyclophosphamide and etoposide/ifosfamide was started alternately for seven cycles. The patient also received radiotherapy to the abdomen and pelvis at 24 Gy. Later, a new cycle was administered to the pelvis at 26 Gy. Thirty months after diagnosis, the patient is under close follow-up and the PET scan has shown no evidence of tumor activity.

Figure 3 A: macroscopic image of the tumor adhered to the jejunal wall. B: after cutting, invasion and destruction of the intestinal wall are observed. 

Discussion

As ES originates from mesenchymal progenitor cells, it has the ability to develop in multiple tissues. The most common clinical manifestation is mild pain that worsens with exercise and at night, including symptoms of spinal cord compression manifested by weakness or loss of sphincter control when the primary lesion is present in an axial location. Constitutional symptoms are present in 10-20% at diagnosis. Symptoms vary depending on the affected area¹. This variation represents a challenge because the clinician must integrate the indolent manifestations until the precise diagnosis.

The final diagnosis always requires histopathological support to confirm the presence of CD99 and EWS-FLI1 (Ewing sarcoma breakpoint region 1/Friend leukemia integration 1 transcription factor) with immunohistochemical studies⁴. Extraosseous presentation of ES is infrequent⁴; most ES are reported in the trunk, head, neck, and extremities²,⁴,⁵. Some studies in the literature have reported ES in the adrenal glands, kidneys, intestine, liver, and peritoneum³,⁴,⁶-¹⁰. Intestinal presentation is more frequent than skeletal ES in adult women. In contrast, no reports were found on intestinal ES in the pediatric age group⁴.

In this patient, the underlying data led to the initial diagnosis of an anemic syndrome with few abdominal symptoms that delayed the diagnosis. Most extraosseous ES can be cured with the combination of chemotherapy, radiotherapy, and surgery; the treatment scheme is decided with the same guidelines as in skeletal ES. The evidence so far indicates that extraosseous involvement is not a poor prognostic factor, as survival is affected by other factors such as the stage of the disease at diagnosis and the resectability of the primary tumor. In most series, the extraosseous presentation was mostly muscular, with greater involvement at the level of the pelvic limbs. Therefore, in the case presented here, the tumor’s location did not play an essential role in the patient’s prognosis. Hence, a 5-year survival of 70% is expected, with an adequate response to the first line of treatment¹.

Extraosseous presentation of ES in pediatric age is rare. Therefore, it requires a multidisciplinary approach to diagnose it accurately. Until now, there are no reports in the Latin American literature of intestinal presentation of ES in the pediatric age group.