First question: is it aggressive?
A bone lesion is assessed systematically using:
- patient age and skeletal maturity
- bone involved
- exact position within the bone
- epiphyseal/metaphyseal/diaphyseal location
- medullary versus surface location
- margin and zone of transition
- pattern of bone destruction
- matrix mineralisation
- cortical response
- periosteal reaction
- soft-tissue mass
- pathological fracture
- multiplicity
Growth rate on radiographs
Broad principles:
- narrow, well-defined margin suggests slower growth
- wide transition zone suggests aggressive biology
- geographic destruction is generally slower than moth-eaten or permeative destruction
- interrupted aggressive periosteal reaction raises concern but is not specific for malignancy
Matrix
- osteoid matrix: cloud-like or dense bone production
- chondroid matrix: rings/arcs or stippled calcification
- fibrous matrix: ground-glass appearance in appropriate lesions
Recognising matrix narrows the differential:
- osteoid mineralisation
- chondroid calcification
- fibrous ground-glass pattern
- absent/minimal visible matrix in some lesions
Soft-tissue mass
A soft-tissue mass that is increasing in size, deep to fascia, painful, recurrent or large should prompt specialist sarcoma assessment rather than unplanned excision.
Staging investigations
When malignancy is suspected, local MRI is used to define the tumour compartment and relationship to neurovascular structures. Systemic staging depends on tumour type and may include CT chest and other investigations directed by the sarcoma MDT.
Biopsy principle
Biopsy is the final step of staging, not the first step of diagnosis.
Plan it with the team that will perform definitive surgery.
The track should:
- use a longitudinal route that can be excised with the tumour
- pass through only one compartment where possible
- avoid contaminating uninvolved neurovascular structures or joints
- place any drain in line with the biopsy incision
Core-needle biopsy is commonly used. Tissue handling is coordinated with pathology.
Avoid the unplanned excision
An inadequately planned biopsy or “shell-out” of an unexpected sarcoma can contaminate compartments and make limb-sparing surgery more difficult.
First principles
A bone lesion should be approached systematically using:
- age
- anatomical site
- exact location within bone
- margin/zone of transition
- matrix
- periosteal response
- cortical change
- soft-tissue mass
- symptoms
- tempo of progression
The radiograph often provides more diagnostic direction than an indiscriminate panel of advanced tests.
History
Ask about:
- duration and progression of pain
- night/rest pain
- swelling
- pathological fracture
- constitutional symptoms
- previous malignancy
- infection
- family history or syndromic features where relevant
Pain alone does not distinguish benign from malignant disease.
Radiographic aggressiveness
Features suggesting a more aggressive lesion include:
- wide zone of transition
- permeative or moth-eaten destruction
- aggressive periosteal reaction
- cortical destruction
- soft-tissue mass
However, infection can mimic malignancy and some malignant lesions can appear deceptively indolent.
Staging
For a suspected primary malignant bone tumour, local MRI defines:
- intraosseous extent
- soft-tissue extension
- neurovascular relation
- skip lesions where applicable
- relationship to joint
Systemic staging commonly includes chest imaging and other tests according to tumour type.
Biopsy principles
Biopsy is part of definitive oncological treatment and should be planned by the team that will perform resection.
Principles:
- biopsy only after appropriate imaging
- choose a tract that can be excised with the definitive specimen
- avoid contaminating uninvolved compartments
- avoid major neurovascular structures
- achieve meticulous haemostasis
- use a longitudinal route where appropriate
- send adequate representative tissue
A poorly planned biopsy can convert a limb-salvageable tumour into a more difficult or non-salvageable problem.
Core biopsy
Image-guided core biopsy is often preferred because it provides architecture with lower morbidity than open biopsy.
Open biopsy is reserved for situations where needle biopsy is inadequate or unsuitable.
Pathology correlation
Diagnosis should be established through multidisciplinary correlation between:
- clinical picture
- imaging
- histology
If pathology and imaging disagree, the discrepancy should be resolved rather than accepting one in isolation.
FRCS synthesis
The essential exam phrase is: image first, stage appropriately, then biopsy through a planned oncological tract.