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

Objective: To comprehensively analyze the spectrum of imaging features of the primary tumors and metastatic patterns of the Extraskeletal Ewing sarcoma family of tumors (EES) in adults. Materials and Methods: We performed a computerized search of our hospital's data-warehouse from 1996 to 2013 using codes for Ewing sarcoma and primitive neuroectodermal tumors as well as the demographic code for ${\geq}18$ years of age. We selected subjects who were histologically confirmed to have Ewing sarcoma of extraskeletal origin. Imaging features of the primary tumor and metastatic disease were evaluated for lesion location, size, enhancement pattern, necrosis, margin, and invasion of adjacent organs. Results: Among the 70 patients (mean age, $35.8{\pm}15.6$ years; range, 18-67 years) included in our study, primary tumors of EES occurred in the soft tissue and extremities (n = 20), abdomen and pelvis (n = 18), thorax (n = 14), paravertebral space (n = 8), head and neck (n = 6), and an unknown primary site (n = 4). Most primary tumors manifested as large and bulky soft-tissue masses (mean size, 9.0 cm; range, 1.3-23.0 cm), frequently invading adjacent organs (45.6%) and showed heterogeneous enhancement (73.7%), a well-defined (66.7%) margin, and partial necrosis/cystic degeneration (81.9%). Notably, 29 patients had metastatic disease detected at their initial diagnosis. The most frequent site of metastasis was lymph nodes (75.9%), followed by bone (31.0%), lung (20.7%), abdominal solid organs (13.8%), peritoneum (13.8%), pleura (6.9%), and brain (3.4%). Conclusion: Primary tumors of EES can occur anywhere and mostly manifest as large and bulky, soft-tissue masses. Lymph nodes are the most frequent metastasis sites.