FEGNOMASHIC

FEGNOMASHIC is a mnemonic for lytic bone lesions popularized by Dr. Clyde Helms, whose textbook shaped the training of an entire generation of radiologists. If you trained in the U.S., you’ve almost certainly encountered it. The letters stand for:

• F — Fibrous dysplasia

• E — Enchondroma

• G — Giant cell tumor

• N — Non-ossifying fibroma

• O — Osteoblastoma

• M — Metastasis / Myeloma

• A — Aneurysmal bone cyst

• S — Simple bone cyst

• H — Hyperparathyroidism (brown tumor)

• I — Infection

• C — Chondroblastoma

In practice, I don’t actually use this mnemonic. It’s hard to keep in your head letter by letter while you’re working, and running through the full list isn’t how experienced radiologists actually think through a lytic lesion. It gets passed down largely because everyone reads Helms — but familiarity isn’t the same as utility.

A more practical approach is to work through the features systematically: Does this look benign or aggressive? Which bone is it in? Where in the bone — epiphysis, metaphysis, diaphysis? Central or eccentric? Is there matrix mineralization? Cortical destruction or soft tissue extension? And how old is the patient? Once you’ve answered those questions, the differential usually shortens considerably on its own. The dedicated topic pages for individual lesions and narrower differential categories will walk through that logic in context.