Onion skin

A lesion or tumor that features concentrically laminated, multilayered pattern resembling onion layers, typically seen in imaging or histology, such as periosteal new bone formation or concentric fibrosis/lamellation around vessels or structures in various pathological conditions. This is seen in bone lesions (Ewing sarcoma, osteosarcoma, Langerhans cell histiocytosis, osteomyelitis), vascular pathology (hyperplastic arteriolosclerosis), lymph nodes (Castleman's disease), perineural pathology (chronic inflammatory demyelinating polyneuropathy, Charcot-Marie-Tooth disease), liver pathology (primary sclerosing cholangitis), and appendix pathology (Low-Grade Appendiceal Mucinous Neoplasms).