Onion skin

A lesion or tumor characterized by a concentrically laminated, multilayered “onion-skin” appearance on imaging or histology, representing repeated layers of tissue deposition, fibrosis, inflammation, or reactive growth around a central structure.

Causes

• Aggressive bone lesions causing reactive periosteal layering

  • Ewing sarcoma: Periosteal new bone formation

  • Osteosarcoma

  • Langerhans cell histiocytosis

  • Osteomyelitis

• Hyperplastic arteriolosclerosis: Proliferation and basement membrane thickening

• Lymph node causes: Castleman disease

• Chronic inflammatory demyelinating polyneuropathy (CIDP)

• Charcot–Marie–Tooth disease: Hereditary demyelinating neuropathy with onion-bulb Schwann cell formations

• Primary sclerosing cholangitis: Concentric periductal fibrosis surrounding bile ducts

• Low-grade appendiceal mucinous neoplasms (LAMN)