Button Sequestrum

A round radiolucent skull defect with a central bony density is referred to as a button sequestrum. This finding can be seen in the following cases, but is an uncommon appearance in all (bold indicates classic cases)

• Langerhans cell histiocytosis: Classic description. Most commonly affects the skull.
• Osteomyelitis
• Fibrosarcoma
• Lymphoma
• Partially calcified intraosseous lipoma
• Tuberculous osteitis
• Radiation necrosis
• Metastatic carcinoma: Especially breast
• Fibrous dysplasia
• Epidermoid and dermoid cysts
• Hemangioma: Mimics button sequestrum.
• Meningioma
• Paget disease
• Multiple myeloma
• Syphilis
• Sarcoidosis

References

• Gamuts in Radiology - Reeder and Felson - 4th ed (Springer, 2003).
• Krasnokutsky MV. The button sequestrum sign. Radiology. 2005 Sep;236(3):1026-7.
• Satin R, Usher MS, Goldenberg M. More causes of button sequestrum. J Can Assoc Radiol. 1976 Dec;27(4):288-9.