Metastases & Myeloma
- In any adult over ~40 with a destructive bone lesion, metastasis or myeloma is the answer until proven otherwise — they are far more common than a primary bone tumor.
- Metastases are usually multiple; the classic primaries are breast, prostate, lung, kidney, and thyroid.
- Metastases come in three flavors: lytic (holes), blastic (white and dense), and mixed.
- Myeloma makes sharply punched-out lytic holes and, unlike most mets, is famously cold on the bone scan — so you screen the skeleton differently.
- The plain radiograph is insensitive: it takes a lot of bone loss before a lytic lesion even shows up, which is why MRI, CT, and PET catch what X-rays miss.
When an adult walks in with a hole in their bone, the most likely culprit is not some exotic primary tumor with a five-syllable name. It's the boring, common, statistically overwhelming pair: cancer that traveled there from somewhere else (metastasis) or a plasma cell gone rogue (myeloma). Bone is prime real estate for wandering tumor cells — it's vascular, marrow-rich, and basically the cheap apartment that every metastatic cell wants to move into.
Why bone is such a popular destination
Tumor cells riding the bloodstream tend to settle where the marrow is busiest — the axial skeleton: spine, pelvis, ribs, skull, and the proximal ends of the femur and humerus. That's where red marrow lingers in adults, and red marrow is the welcome mat. So when you go hunting, look central first. A lesion way out in the hand or foot is unusual for a met (though lung cancer is the troublemaker that occasionally does it).
The single most important reflex: if you see one destructive lesion in an older adult, assume there are more and go look. Mets travel in packs.
A solitary aggressive-looking bone lesion in an adult over 40 should make you think metastasis or myeloma first — not a rare primary sarcoma. Common things are common.
Lytic, blastic, or mixed — reading the color
Metastases destroy bone in one of three ways, and the pattern hints at the primary.
| Pattern | What it looks like | Classic primaries |
|---|---|---|
| Lytic | Dark holes — bone eaten away | Kidney, thyroid, lung, breast (and most others) |
| Blastic | Dense, ivory-white deposits | Prostate; some breast |
| Mixed | Both at once | Breast is the great mimic — can do any pattern |
A useful mental shorthand: lytic mets are the demolition crew (kidney and thyroid lesions can be aggressively destructive and even expansile, ballooning the bone out), while blastic mets are the over-eager construction crew laying down too much dense, useless bone. Prostate is the poster child for the white, sclerotic kind.
Myeloma: the punched-out impostor
Multiple myeloma is a malignancy of plasma cells, and on imaging it loves to make multiple small, sharply marginated lytic lesions — the classic "punched-out" look, as if someone took a hole-punch to the skull and spine. It can also just diffusely thin the bones until they look washed-out and osteopenic.
Here's the trap worth tattooing on the inside of your eyelids:
Multiple myeloma is typically cold (negative) on a conventional bone scan. A bone scan lights up where bone is trying to repair itself; myeloma is so purely destructive that the bone doesn't mount that reaction. So a normal bone scan does not rule out myeloma. Screen the marrow with a skeletal survey, whole-body low-dose CT, MRI, or FDG-PET instead.
This is the opposite of most metastases, which usually do provoke a repair response and therefore do light up on a bone scan. The lone exception that proves the rule: very lytic mets (think renal cell) can also be quiet on a bone scan for the same reason myeloma is.
Why the X-ray under-promises
A plain radiograph is reassuringly cheap and frustratingly insensitive for marrow disease. A lytic lesion has to destroy a substantial fraction of the trabecular bone before your eye can register the lucency — so a "normal" X-ray buys you almost nothing in a patient you're genuinely worried about. MRI sees the marrow being replaced long before the cortex crumbles; CT shows subtle cortical breakthrough; FDG-PET shows the metabolic activity. Match the test to the question.
This page assumes you already know how to size up a lesion's aggressiveness. If the words zone of transition or periosteal reaction make you squint, detour through how to approach a bone lesion and the aggressive-versus-not framework first.
The complication that makes this urgent
The reason mets and myeloma aren't just an academic naming exercise: weakened bone breaks. A pathologic fracture through a metastatic or myelomatous lesion can happen with trivial force, and in the spine it can collapse a vertebra and threaten the cord. When a met eats away enough of a long bone's cortex, surgeons step in to fix it before it snaps — so flagging an at-risk lesion is a genuine save, not a formality.
When you find one bone lesion, your report isn't done until you've answered three questions: Are there others? Is the cortex breached enough to risk fracture? And is the spine involved in a way that could threaten the cord? Those three lines change management.
The one thing to remember
In an adult, a destructive bone lesion is metastasis or myeloma until proven otherwise. Mets are usually multiple and follow the marrow; their lytic-versus-blastic flavor hints at the primary. Myeloma punches clean holes and hides from the bone scan. And the plain film is the least sensitive tool in the box — when you're worried, reach for marrow-sensitive imaging.