Polyostotic Bone Lesions

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Definition. Polyostotic disease means two or more separate bones carry lesions, or a single bone carries widely separated non-contiguous lesions. This is distinct from multifocal within one bone (skip lesions) and from diffuse marrow replacement, where the marrow signal is abnormal throughout without discrete lesions.

Confirming the pattern is genuine. Before committing, satisfy yourself that:

• The lesions are in bone, not overlying soft tissue, bowel gas or a skin marker. Repeat the film with a marker if the lesion moves.
• The lesions are real, not composite shadows — sacral foramina, the trochanteric fossa, the herald patch of a ribbon rib, and vascular grooves in the skull all mimic lucency on a single projection. Orthogonal views resolve most.
• The normal variants are excluded: pseudocysts of the humeral head and calcaneus (the neutral triangle), Ward's triangle in the femoral neck, and the pelvic digit are all trabecular rarefaction, not lesion.

How to say it out loud. "This is a radiograph of the pelvis and both femora in a skeletally mature patient. There are multiple well-defined lytic lesions involving the iliac wings and both proximal femora. They are geographic with a narrow zone of transition, there is no matrix mineralisation, no periosteal reaction and no soft tissue mass. The distribution is axial and proximal appendicular, which corresponds to red marrow. In a patient over 40 my primary concerns are metastatic disease and myeloma, and I would want to exclude hyperparathyroidism."

Then commit to a lead diagnosis. Never end a description without one.

Mimics of the pattern (false positives).

• Multiple non-ossifying fibromas in an adolescent — eccentric, cortically based, sclerotic rim, asymptomatic; if numerous plus café-au-lait think Jaffe-Campanacci.
• Bone islands (enostoses) — dense, brush-bordered, cold on bone scan; the osteopoikilosis pattern gives symmetric periarticular dense foci and is a normal-life-expectancy sclerosing dysplasia.
• Fat-containing marrow (haemangioma, focal red marrow rests) — vertebral corduroy or polka-dot pattern; red marrow rests follow marrow signal on all sequences and lack restricted diffusion.
• Insufficiency fractures in the sacrum and pubic rami of an osteoporotic patient can look like multiple lucencies or, on bone scan, the Honda sign — a fracture pattern, not lesions.
• Degenerative subchondral cysts and gouty erosions cluster at joints and communicate with articular surfaces.

Related pages. The two that own the adult over 40: Metastatic Bone Disease and Multiple Myeloma — plus Multiple Myeloma of the Spine for the commonest symptomatic site. The one that expands the bone: Paget's Disease of Bone, and Paget's Sarcoma when a Pagetic bone starts to destroy rather than enlarge. The biochemical mimic that must be excluded before any biopsy: Hyperparathyroidism and Renal Osteodystrophy. The young skeleton: Fibrous Dysplasia with McCune-Albright Syndrome, Langerhans Cell Histiocytosis, Non-Ossifying Fibroma, and Multiple Hereditary Exostoses with Osteochondroma. The cartilage group and what it becomes: Enchondroma, Enchondromatosis (Ollier's), Maffucci Syndrome and Chondrosarcoma — the transformation the surgical caution above is about. Multiplicity that is still malignant: Osteosarcoma, Ewing Sarcoma and Primary Bone Lymphoma. Infection and its sterile counterpart: Osteomyelitis Pathophysiology and Chronic Recurrent Multifocal Osteomyelitis. Before the needle goes in: Biopsy Principles and Techniques.