Eight year old girl with large abdominal mass.
Large FDG-avid mass occupying majority of abdomen (SUVmax 10) with areas of hypometabolism suggestive of necrosis. The mass does not seem to arise from adrenals, kidneys, liver, spleen or muscle. It is difficult to distinguish the pancreas from the mass. There are multiple liver active lesions suspicious for metastatic process. Bilateral pleural effusion without significant uptake.
High grade sarcoma
Germ cell tumor
Metastatic extraskeletal Ewing's sarcoma
The Ewing’s sarcoma family of tumors includes Ewing’s sarcoma of bone (ESB), extraskeletal Ewing’s sarcoma (EES), peripheral primitive neuroectodermal tumor of bone (pPNET) and Askin tumor (extraskeletal Ewing’s sarcoma of the chest wall). They are neoplasms of neuroectodermal origin. Initially, they were thought to be distinct neoplasms, but the current consensus is that they arise from a common precursor cell. Histopathologically, the distinction is based on cellular differentiation: Ewing’s sarcoma (ESB and EES) shows minimal differentiation while pPNET demonstrates some degree of neuroectodermal differentiation. These tumors are characterized cytogenetically by a translocation between the long arms of chromosomes 11 and 22 (t[11;22][q24;q12]), which is present in approximately 90% of these lesions.
EES is rare in comparison with ESB. Frequently, patients present with a large and rapidly growing mass. According to Murphey et al., the most commonly reported locations of extraskeletal Ewing’s sarcoma include the paravertebral region (32%), lower extremities (26%), chest wall (18%), retroperitoneum (11%), pelvis and hip (11%), and upper extremities (3%).
Like in ESB, PET FDG is useful the initial staging as well as detection of recurrence.
The differential diagnosis for an abdominal mass in a child is wide. Abdominal masses are most often found in children less than 5 years of age. Neuroblastoma is the most common malignant abdominal tumor in this range of age. Another common abdominal malignancy is Wilm’s tumor. Less common tumors include soft tissue (rhabdomyosarcoma and non rhabdomyosarcoma) sarcomas, germ cell tumors, and hepatoblastoma. Beyond infancy, Wilm's tumor, sarcomas, lymphoma and germ cell tumors predominate. In children over than 10 years of age, the incidence of neuroblastoma and Wilm’s tumor decrease but sarcomas, germ cell tumors and abdominal lymphomas become more frequent.
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Huh J et al : Imaging Features of Primary Tumors and Metastatic Patterns of the Extraskeletal Ewing Sarcoma Family of Tumors in Adults: A 17-Year Experience at a Single Institution. Korean J Radiol. 2015 Jul-Aug; 16(4): 783–790
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Golden CB et al : Malignant abdominal masses in children: quick guide to evaluation and diagnosis. Pediatr Clin North Am. 2002 Dec;49(6):1369-92