|Ahead of print publication
Cytological diagnosis of Extraskeletal Ewing's sarcoma
Ashwini Amrutwar, Sunil Yogiraj Swami
Department of Pathology, S.R.T.R. Government Medical College, Beed, Maharashtra, India
|Date of Submission||20-Feb-2020|
|Date of Decision||13-Apr-2020|
|Date of Acceptance||24-Jun-2020|
Sunil Yogiraj Swami,
Bhagwanbaba Chowk, Gitta Road, Shepwadi, Ambajogai Taluk, Beed District - 431 517, Maharashtra
Source of Support: None, Conflict of Interest: None
Extraskeletal Ewing's sarcoma (ES) is an aggressive, malignant small round-cell tumor usually occurring in children and adolescents. It needs to be differentiated from other malignant small round-cell tumors. Immunohistochemistry plays a pivotal role in establishing the diagnosis. ES/peripheral primitive neuroectodermal tumor is presumed to be neuroectodermal in children and young adults.
Keywords: Cytology, diagnosis, Ewing's sarcoma
| Introduction|| |
Extraskeletal Ewing's sarcoma (ES) is a rare subtype within the ES family of tumors (ESFT). These are small round-cell tumors showing a varying degree of neuroectodermal differentiation., It is composed of sheets of small cells with high nucleus-to-cytoplasm ratio. The cytoplasm is scant, eosinophilic, and usually contains glycogen, which is detected by periodic acid–Schiff (PAS) stain and is diastase degradable. The nuclei are round, with finely dispersed chromatin and one or more tiny nucleoli. Occasional rosette formation is also seen. This tumor frequently undergoes necrosis, and the residual viable cells show a peritheliomatous distribution. Depending on the degree of neuroectodermal differentiation, the tumor cells may also express neuron-specific enolase, synaptophysin, and S-100 protein. Immunohistochemistry (IHC) is essential as the family of small round-cell tumors is rather large and includes non-Hodgkin's lymphoma, neuroblastoma, rhabdomyosarcoma, mesenchymal chondrosarcoma, retinoblastoma, and desmoplastic small round-cell tumor. Other tumors can also show small round cells, and these are osteosarcoma, synovial sarcoma, malignant peripheral nerve sheath tumor, and melanoma.
| Case Report|| |
A 17-year-old female presented with complaints of pain and swelling over the right leg for 5–6 months. On gross examination, a well-defined lump measuring 2 cm × 3 cm, firm, nontender with smooth surface was noticed over the right leg. X-ray [Figure 1] revealed soft tissue lesion with destruction of adjacent bone and mottled appearance. Fine-needle aspiration cytology (FNAC) [Figure 2] revealed a monomorphic population of small round cells in the background of hemorrhage, showing occasional rosette formation. PAS stain revealed PAS-positive presence of intracytoplasmic glycogen [Figure 3]. Histopathology revealed infiltrating tumor composed of sheets of small round cells [Figure 4]. IHC showed strong positivity for CD99 (MIC-2) and FLI-1. The tumor cells show weak focal staining for synaptophysin. The tumor cells were negative for desmin, Leukocyte common antigen (LCA), TdT, pancytokeratin, S-100, and Bcl2. A final diagnosis of extraskeletal ES with the involvement of the adjacent bone was made.
|Figure 1: Predominant extraskeletal soft tissue lesion with bony erosion (X-ray: Right leg: Lateral view)|
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|Figure 2: Cellular smear showing dispersed, small, monomorphic round cell with fine nuclear chromatin and round nuclei and scanty clear cytoplasm. Rosette formation was also noted (Pap, ×40)|
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|Figure 3: Cytoplasmic periodic acid–Schiff positivity in small round cells (PAS, ×40)|
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|Figure 4: Biopsy showing sheets of small, round, uniform cells divided into irregular lobules by fibrous strands (H and E, ×40)|
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| Conclusion|| |
James Ewing described the first case of ES in 1921. It is usually seen in the age group of 5–30 years with a peak incidence at 10–15 years. The male-to-female ratio is 3:2. It is highly aggressive tumor which is PAS and CD99 (MIC2) positive with relatively a few variant translocations been reported in primary ES. Although it can involve any bone, it is more common in the bones of the lower extremity. ES is highly malignant round-cell tumor and has aggressive clinical behavior and distant metastasis. ESFTs represent a family of malignant small round-cell neoplasms, ES of the bone, primitive neuroectodermal tumor, extraskeletal ES, and Askin tumor. ESFTs generally originate in bone tissue, but they can occasionally originate in soft tissue, known as ES, which constitutes 6%–47% of all ESFTs and 1.1% of all malignant soft tissue tumors. Extraskeletal ES has a poorer prognosis as compared to its osseous counterpart, with high incidence of local recurrence and distant metastasis.
ES is characterized by balanced translocations between the EWS gene and the ETS family members such as FLI1 and EWG. Approximately 85% of cases have the t(11;22)(q24;q12) translocation.
FNAC is a very economic and quick procedure in the diagnosis of ESFT. Accurate diagnosis on cytology can be made in the extraskeletal ES as in our case by adequate material, radiological guidance, cytomorphology, and special stain such as PAS. However, IHC is essential for confirmation of the diagnosis.
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.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]