Lucent/lytic bone lesion - differential diagnosis (mnemonic)

Last revised by Dr Rohit Sharma on 11 May 2022

Mnemonics for the differential diagnosis of lucent/lytic bone lesions include:

  • FEGNOMASHIC
  • FOG MACHINES

They are anagrams of each other and therefore include the same components. They are by no means exhaustive lists, but are a good start for remembering a differential for a lucent/lytic bone lesion and will suffice for >95% of the time 1.

Mnemonics

FEGNOMASHIC
FOG MACHINES
  • F: fibrous dysplasia (FD) or fibrous cortical defect (FCD)
  • O: osteoblastoma
  • G: giant cell tumor (GCT) or geode
  • M: metastasis(es)/myeloma
  • A: aneurysmal bone cyst (ABC)
  • C: chondroblastoma or chondromyxoid fibroma
  • H: hyperparathyroidism (brown tumor)
  • I: infection (osteomyelitis) or infarction (bone infarction)
  • N: non-ossifying fibroma (NOF)
  • E: enchondroma or eosinophilic granuloma (EG)
  • S: simple (unicameral) bone cyst

These lists are not exhaustive (e.g. intraosseous lipoma is omitted)

History and etymology

The earliest reference to FEGNOMASHIC in the literature seems to be from a paper published by a group of radiologists at University of California in 1972, which was itself based on work presented at the Scientific Assembly and Annual Meeting of the Radiological Society of North America in 1971. Its invention likely predates this, however its origin remains obscure. It was certainly not invented by the renowned musculoskeletal radiologist Clyde Helms, as some claim, not least because Helms himself stated that he was taught it whilst in the Air Force, before he had even started his radiology residency 1,3!

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Cases and figures

  • Case 1: Metastasis - RCC
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  • Case 2: Multiple myeloma - skeletal survey
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  • Case 3: Multiple myeloma - skeletal survey
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  • Case 4: Aneurysmal bone cyst
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  • Case 5: Giant cell tumor
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  • Case 6: Giant cell tumor
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  • Case 7: Enchondroma
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  • Case 8: Aneurysmal bone cyst (ABC) - tibia
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  • Case 9: Osteoblastoma
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