Clinical Profile:

A 67 year old woman came with pain in the left side of the abdomen since six months. Se also gives history of early satiety since three months. Abdominal examination showed a  freely mobile, lump on the left side - all borders were palpable. The deeper extent of the lesion could not be felt. 

Radiological findings:

The sonogram shows a large, vascular, heterogeneously hypoechoic solid lesion with in the left hypochondrium extending till the umbilicus.(Fig. 1)

Fig. 2 : Axial and coronal sections of CT abdomen and pelvis shows a large well defined, heterogeneously enhancing soft tissue lesion arising from the retroperitoneum on the left side measuring approx. carotid space measuring approximately 12.0x10.8x11.5cm (APxTRxCC). The lesion is causing mass effect in the form of compression of adjacent structures like displacing the left kidney postero-laterally. Pancreas anteriorly.

The MRI of the abdomen and pelvis shows a large retroperitoneal lesion on the left side measuring 12.6x12.8x14.7 cm. It is T2 iso to hyperintense, T1 hypointense with central T2 hypointense and T1 iso to hyperintense area.. The central necrotic component of the lesion shows diffusion restriction. No calcification or fat was seen within the lesion. There is posterolateral displacement of the left kidney and mild compression of the PUJ.

Fig, 3 : Axial and coronal sections of MRI abdomen shows a large heterogenous T2 iso to hyperintense, T1 hypointense mass lesion with central T2 hypointense and T1 iso to hyperintense area is seen in the retroperitoneum on the left side measuring 12.6x12.8x14.7 cm (APXTRXCC). The central necrotic component of the lesion shows diffusion restriction. No calcification or fat within the lesion. There is mass effect in the form of posterolateral displacement of left kidney and mild compression of the PUJ causing its compression.

Histopathological diagnosis: 

Percutaneous, ultrasound guided biopsy of the lesion was performed 

The histopathological findings were interpreted as an Extraosseous Ewing’s sarcoma

Treatment: 

The patient is currently undergoing neoadjuvant chemotherapy to downstage the tumour before surgery.

Fig. 4 : Histopathology of the tumour shows sheets of uniform small round blue cells

Timeline :

Discussion:

Ewing sarcoma (ES) is a round cell tumor, highly malignant and poorly differentiated that is currently the second most common malignant bone tumor in children.  In rare instances, it develops from an extraskeletal origin, classified as extraosseous Ewing sarcoma (EES) (1).

• It is usually found in older children and adolescents compared to Ewing sarcoma from bone origin in the pediatric population. 

• EES is also present in a bimodal distribution and is more commonly found in patients less than five years old and older than 35 compared with ES . 

• Extraskeletal involvement includes: Head and neck, retroperitoneum, omentum, paravertebral, orbits, skin, chest wall, pelvis and lower extremities. EES has also been reported to arise in the gastrointestinal tract, including: Pancreas, omentum, kidney and adrenals 

• Askin tumor, also known as thoracopulmonary PNET , is the single most common presentation of extraskeletal ESFT. A large chest wall mass with intrathoracic extension is typical. Tumors vary in aggressiveness. Some destroy adjacent ribs and invade pulmonary parenchyma; others may only cause periosteal reaction and displace the lung

• Ewing sarcoma shares with peripheral primitive neuroectodermal tumor (pPNET) a balanced translocation t(11;22) (q24;q12) in over 85% of cases; however, they comprise a different spectrum of the same histological group of neoplasms encompassed in the term Ewing sarcoma family tumor (ESFT).

• Histology of tumors in this family is currently classified as “classical”, or “variant”. Classical ES is the prototypic undifferentiated small round cell tumor characterized by round oval sheet cells with primitive nuclei and clear cytoplasm. Atypical histology is characterized by large and pleomorphic cells with irregular nuclear membranes with clear eosinophilic cytoplasm. 

• There are numerous variant histological types with distinct morphologic features that classify them into: Large cell, pPNET, adamantinoma-like, spindle cell sarcoma-like, sclerosing and vascular-like. 

• Plain radiograph shows normal appearance to large soft-tissue mass with calcification and presence of adjacent bone erosion, cortical thickening, osseous invasion, or periosteal reaction.

• CT shows nonspecific soft-tissue mass of similar attenuation to the muscle , low attenuation can be due to hemorrhage or necrosis. calcification with osseous involvement of bone surface with cortical erosion or periosteal reaction  

• MRI shows A common feature of disorganized high-flow vascular channels with low signal intensity with all pulse sequences. Additionally, a pseudocapsule with somewhat well-defined margins can be seen. 

T1 - soft tissue mass with heterogeneous signal intensity similar to skeletal muscle

           T1 C+ (Gd)- heterogeneous but prominent enhancement

     T2 - intermediate to high signal intensity. Fluid levels may be evident

General imaging differential considerations include (2):

• Higher grade vascular lesions (hemangioendothelioma, hemangiopericytoma, angiosarcoma)

• Rhabdomyosarcoma

• Synovial sarcoma

• Alveolar soft-part sarcoma

Treatment options include (3):

 Neoadjuvant chemotherapy is the standard of care before definitive radiation or surgery for localized disease. 

In all cases, however, micrometastases should be assumed, and the standard regimen will include some combination of vincristine, doxorubicin, ifosfamide, etoposide, and cyclophosphamide with treatment based on pediatric experiences

References:

1. Gurria JP, Dasgupta R. Rhabdomyosarcoma and Extraosseous Ewing Sarcoma. Children (Basel). 2018 Dec 10;5(12):165. doi: 10.3390/children5120165. PMID: 30544742; PMCID: PMC6306718.

2. Pearson B, Saber M, Feger J, et al. Extraskeletal Ewing sarcoma. Reference article, Radiopaedia.org (Accessed on 20 Jul 2023) https://doi.org/10.53347/rID-36534

3. A to Z of Extraskeletal Ewing Sarcoma Family of Tumors in Adults: Imaging Features of Primary Disease, Metastatic Patterns, and Treatment Responses. Omar Javery, Katherine Krajewski, Kevin O’Regan, Bela Kis, Angela Giardino, Jyothi Jagannathan, and Nikhil H. Ramaiya.doi.org/10.2214/AJR.11.6667

4. Alexander A, Hunter K, Rubin M, Bhat AP. Extraosseous Ewing's Sarcoma: Pictorial Review of Imaging Findings, Differential Diagnosis, and Pathologic Correlation. Indian J Radiol Imaging. 2021 Jan;31(1):203-209. doi: 10.1055/s-0041-1729770. Epub 2021 May 31. PMID: 34316128; PMCID: PMC8299506.   

5. A Rare Case of Intraabdominal Extraosseous Ewing Sarcoma Involving the Small Bowel Mesentery. Krupa KM; Kriley IR; Williams HK

Acknowledgement :

We are grateful to the Department of Pathology  at our institution for providing us with an image from the histological findings as also its description.