Indian Journal of Pathology and Microbiology

: 2018  |  Volume : 61  |  Issue : 2  |  Page : 248--251

A mesenteric primary peripheral Ewing's sarcoma/primitive neuroectodermal tumor with molecular cytogenetic analysis: Report of a rare case and review of literature

Yi-Shu Liao1, I-Han Chiang2, Hong-Wei Gao3,  
1 Department of Pathology, Taichung Armed Forces General Hospital, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan, ROC
2 Department of Pathology, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan, ROC
3 Department of Surgery, Division of Plastic and Reconstructive Surgery, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan, ROC

Correspondence Address:
Hong-Wei Gao
Department of Pathology, Tri-Service General Hospital, National Defense Medical Center, 3F., No. 325, Sec. 2, Chenggong Rd., Neihu Dist., Taipei City 114, Taiwan


Rare cases of Ewing's sarcoma/primitive neuroectodermal tumors (EWS/PNETs) arising from mesenteric tissue have been reported. This report describes an EWS/PNET in a 25-year-old woman who presented with abdominal pain lasting 3 days. Radiologic evaluation revealed a 9 cm × 6 cm homogeneous mass in the lower abdomen with homogeneous enhancement and invasion of the ileum. Surgical resection was completed during exploratory laparotomy. Immunohistochemically, the tumor cells revealed CD99, friend leukemia virus integration-1 and NKX2.2 (NK2 Homeobox 2, a protein coding gene) and subsequently showed EWSR1 rearrangement. The histological feature, immunohistochemical results and genetic fluorescence in situ hybridization analysis of this case were confirming the diagnosis of EWS/PNET. Adjuvant chemotherapy was suggested, but the patient was lost to follow-up.

How to cite this article:
Liao YS, Chiang IH, Gao HW. A mesenteric primary peripheral Ewing's sarcoma/primitive neuroectodermal tumor with molecular cytogenetic analysis: Report of a rare case and review of literature.Indian J Pathol Microbiol 2018;61:248-251

How to cite this URL:
Liao YS, Chiang IH, Gao HW. A mesenteric primary peripheral Ewing's sarcoma/primitive neuroectodermal tumor with molecular cytogenetic analysis: Report of a rare case and review of literature. Indian J Pathol Microbiol [serial online] 2018 [cited 2020 Apr 1 ];61:248-251
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Full Text


Ewing's sarcoma/primitive neuroectodermal tumors (EWS/PNET) are malignant soft-tissue tumors occurring most commonly in the bones in children but increasingly common in the soft-tissues in young adult. Nearly 90% of ES/PNET have a genetic EWS-friend leukemia virus integration-1 (FLI1) fusion protein which results from a specific t (11;22). The carboxy-terminus of FLI1 in immunochemical stain is sensitive and extremely specific for the diagnosis of ES/PNET.[1] ES/PNET is uncommon in the mesenteric area. It is objectively confirmed by the immunohistochemical stains and molecular analysis. There are only 36 cases of intestinal EWS/PNET have been previously documented and the author has collected all previous cases of a published report of intestinal ES/PNET in [Table 1]. Therapeutically, the earlier published cases were almost treated with operation and adjuvant computed tomography (CT), and with elective radiotherapy in some cases.{Table 1}

 Case Report

Ms. B is a 25-year-old woman presented to the author's department reporting abdominal tenderness and poor appetite for the past 3 days. She was afebrile and denied any history of the systemic disease or traumatic surgery, and she had well oriented and conscious on general physical examination. Her laboratory tests were all within normal limits, and tumor markers including carcinoembryonic antigen and cancer antigen 19–9 were standard. Abdominal CT showed a homogenous 9 cm × 6 cm mass in the lower abdomen with the invasion of the ileum [Figure 1]a. The clinically and radiologically differential diagnoses included gastrointestinal stromal tumor, lymphoma, and leiomyosarcoma. Given that malignancy was suspected, she underwent exploratory laparotomy.{Figure 1}

Exploratory laparotomy identified the tumor about 40 cm from the lower region of the ligament of Treitz. The specimen revealed a solid homogenous tumor mass measured 9.2 cm × 5.9 cm × 4 cm in the lower abdomen with an invasion of the ileum [Figure 1]b.

Under the histological examination of the tumor, hypercellular monomorphic small blue round cells with scant cytoplasm and focal clearing of the cytoplasm were arranged in sheets and compact nest patterns microscopically [Figure 2]a. The tumor cells lacked well-formed rosettes. The round-to-oval nuclei had finely distributed chromatin and a small nucleolus [Figure 2]b. Mitotic figures were infrequent. Besides, foci of necrosis, hemorrhage, and edema within the tumor were noted. The initial differential diagnoses included small cell carcinoma, lymphoma/leukemia, synovial sarcoma, EWS/PNET, neuroblastoma, alveolar rhabdomyosarcoma, and desmoplastic small round cell tumor.{Figure 2}

A panel of immunochemical markers revealed that the tumor cells were positive for vimentin, CD99, FLI1, and NKX2.2 expressed in a membranous fashion for CD99 and showing nuclear reactivity for NKX2.2 [Figure 3]a and b] as well as nuclear reactivity for FLI1 [Figure 3]c. Staining for the other markers, including leukocyte common antigen markers and neuroendocrine markers, were all negative.[2],[3] A genetic fluorescence in situ hybridization (FISH) analysis for the EWSR1gene showed a break-apart signal pattern and revealed a t (11–22) translocation of the tumor cells, indicating a translocation involving the EWS gene [Figure 4].[4] Adjuvant chemotherapy was suggested; however, Ms. B defaulted for any further treatment, and she was lost to follow-up.{Figure 3}{Figure 4}


EWS/PNET usually occurs in the soft tissues, bones, or central nervous system as a sporadic aggressive malignant small round cell tumor. EWS/PNET were first documented by Stout in 1918.[5] EWS/PNETs can be classified into two main groups: central EWS/PNET that grow from the central nervous system and peripheral pEWS/PNET that grow somewhere outside the central nervous system.[6] EWS/PNETs are generally identified in children and young adults along the central axis, mostly in the soft tissue or bone. This aggressive and unusual tumor has been seen in the esophagus, liver, pancreas, adrenal gland, kidneys, prostate, urinary bladder, and gynecological organs.[7]

To the best of our knowledge, only 36 cases of intestinal EWS/PNET have been previously documented. In summary, the author has collected all previous cases of a published report of intestinal ES/PNET in [Table 1]. The small intestine besides the mesentery is the most common location, followed by the mesocolon and duodenum. The current study reveals another rare area, i.e., the ileocecum.[8]

Currently, there are no blood markers reported to be helpful for diagnosing EWS/PNET. The histologic manifestation of the tumor typically consists of round-to-ovoid hyperchromatic cells with little cytoplasm, arranged in a solid nest growth pattern with varying rosette-like formations. It is possible to distinguish EWS/PNETs from other small round-cell tumors by immunohistochemical stains and molecular analysis; however, it is hard to differentiate EWS/PNET from other small blue round blue cell tumors.[9]

The FISH analysis of EWS/PNET in our case revealed the rearrangement of the EWSR1 gene. Mhawech-Fauceglia et al. proved that a combination of CD99 and FLI1 is the most sensitive and specific test panel for the diagnosis of EWS/PNET.[6] Recently, Yoshida et al. reported that a significant target of EWS-FLI1, the NKX2.2 gene, is a useful marker for EWS/PNET, with a sensitivity of 93% and a specificity of 89%.[3] The genetic feature is the occurrence of a specific translocation, t (11; 22) (q24; q12), revealed in 90%–95% of patients, which is critical for an accurate diagnosis, selection of the most favorable treatment, and prognosis.[2],[4],[10] Currently, there is no preferred conventional treatment modality for intestinal EWS/PNET. Complete surgical excision provides the greatest chance of survival, and adjuvant radiotherapy may decrease local recurrence. Li et al.'s demographic research has indicated that EWS is far less frequent in Asian than in the United States Caucasian population. Nevertheless, whether the result is associated with genetic background differences still needed to be studied.[7]

In conclusion, we have reported for the first time an unusual case of mesenteric localized ES/PNET in the Asian population, as confirmed by histopathologic examination and genetic analyses. The present case, together with previous studies, has expanded the spectrum of the tumor in the small intestine and the absence of metastasis of this patient is the critical fact in the Ms. B's prognosis.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.


The genetic FISH analysis and evaluation were graciously provided by H.Y. Huang, PhD, Chang Gung Memorial Hospital-Kaohsiung Medical Center, Department of Pathology. Informed consent was obtained from the patient and the applicable Institutional Review Boards/Ethical Committees.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.


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