Imaging features of Ewing's sarcoma: Special reference to uncommon features and rare sites of presentation

Ewing's sarcoma (EWS) commonly involves long bones with a permeative pattern of bone destruction and aggressive interrupted periosteal new bone formation. However, radiological features show wide variation and some presentations are uncommon, leading to diagnostic confusion. This study is aimed at studying the imaging features of proven EWS and highlight the uncommon features and rare sites of presentation.

The imaging findings of 100 consecutive histopathologically proven EWS were analyzed retrospectively. All uncommon presentations with respect to age and site and morphology of lesion were observed.

Most of the patients were below 20 years of age and 8% were younger than 5 years. Other than long bones, ribs, and pelvis, other sites considered to be rare and were noted in 25%. Extraosseous site involvement was 11%. Uncommon features included epiphyseal involvement (4%), sclerosis (4%), expansion of bone (8%), sunray spiculation (10%), calcification in soft tissue (8%), saucerization (4%), pathological fracture (5%), fluid-fluid level (2%), vertebra plana (2%), and lesion crossing the joint (13%).

The uncommon observations included incidence in children <5 years (8%) and occurrence in craniofacial bones, spine, scapula, and clavicles and in extraosseous sites such as retroperitoneum, adrenals, or extremity. Uncommon findings included epiphyseal involvement, sclerosis, saucerization, calcification in soft tissue component, and pathological fracture and lesion crossing the joint.