Onion Skin Sign

James Ewing’s original description ¹ (1921) of the diffuse endothelioma of bone, that is now called Ewing’s tumor, did not include the pungent term (onion skin) later used to depict the layers of periosteal reaction often seen when this tumor penetrates the cortex of a long bone (Figure 1). Ernest Amory Codman ² did use the term in his 1925 article that presented the ‘official nomenclature’ of the Registry of Bone Sarcoma, when he said, ‘Roentgenologically it shows a characteristic longitudinal striation and the tumor nearly always involves more than half of the shaft. It does not often produce the radiating spicules, [see Sunburst sign] but there may be onion-like layers of periosteal new-bone formation such as one sees in osteomyelitis.’ ² We do not know which of the contributors* to the ‘official nomenclature’ first used the term in reference to Ewing’s tumor. Ewing (1866–1943) never uses it in any of the editions of his book, Neoplastic Diseases; A Treatise on Tumors’. The latest edition appeared in 1940. Regarding the name ‘Ewing’s tumor’ Codman said, ‘As a matter of classification we carry this tumor under Ewing’s name, rather against his will and more or less to his mortification, because he not infrequently disowns a tumor which the Registrar [Codman] tries to place under his name.’ ² Figure 1 The five layers of periosteal new bone produce the classic onion-peel appearance.’ Reprinted from <italic>The Bones and Joints</italic> by <xref ref-type="bibr" rid="ref59_6">Lodwick (1971)</xref> <xref ref-type="bibr" rid="ref59_5"> ⁵ </xref>, published by Year Book Medical Publishers. Chicago. Copyright 1971 with ACR. Reprinted with permission https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781003076568/34c29fd5-5662-4e8f-b58c-badd7fa5d724/content/fig59_1_B.jpg"/>