Synonyms

• BPOP
• Nora lesion

Category

Bone

Behaviour

Benign

Gender

Both equally

Tissue of Origin

Bone

Epidemiology

• Rare reactive/neoplastic lesion of Bone surface
• Wide age range, peak 3rd–4th decade
• No sex predilection
• Often associated with prior trauma

Clinical Features

• Painful swelling on Bone surface
• Rapid growth raising concern for malignancy
• No systemic symptoms
• May recur locally after excision

Location

• Small Bones of hands and feet most common
• Distal phalanges of fingers
• Rarely long Bones or skull

Imaging

• Pedunculated or sessile surface lesion
• Mineralised matrix (calcified Cartilage and Bone)
• No cortical destruction
• CT shows dense mineralisation arising from cortical surface

Pathology

• Bizarre Cartilage with hypercellularity and nuclear atypia
• Mineralising Fibrous tissue
• 'Blue' Cartilage (basophilic myxoid matrix)
• No continuity with medullary canal (unlike osteochondroma)

Genetics

• t(1;17)(q32-42;q21-23) translocation reported in some cases
• COL6A3-USP6 fusion described
• Uncertain whether neoplastic or reactive

Treatment

• Local excision - marginal or intralesional
• High recurrence rate (50–55%) - multiple excisions may be required
• No Malignant transformation reported

Prognosis

• Benign but locally aggressive with High recurrence rate
• No metastatic potential
• Repeated excisions may be needed

Key Points

• Cytological atypia mimics malignancy but behaviour is Benign
• Lack of medullary continuity distinguishes from osteochondroma
• USP6 rearrangement links it to nodular fasciitis (reactive vs neoplastic debate)
• Recurrence in >50% after simple excision

Workup - Blood Tests

FBC, U&E, LFTs - pre-operative baseline

Workup - Local Imaging

• Plain radiograph - mineralised surface lesion; no medullary continuity
• CT primary site - characterises mineralisation, confirms no cortical destruction
• MRI - if soft tissue extension or malignancy suspected

Workup - Biopsy

• Excision biopsy preferred - complete removal diagnostic and therapeutic
• Histology: 'blue Bone' (basophilic Cartilage), hypercellular with nuclear atypia, no necrosis
• USP6 FISH - rearrangement supports diagnosis in atypical cases
• Exclude parosteal osteosarcoma: MDM2/CDK4 FISH negative in BPOP

Workup - Staging

No staging required

Workup - Other

MDT discussion if imaging ambiguous - exclude parosteal osteosarcoma before excision

Follow-up Summary

• Post-op visit at 6 weeks; plain X-ray + CT of primary site as new baseline
• Year 1–2: 6-monthly clinical review + plain X-ray of affected site
• If recurrence detected (>50% rate): re-excision; continue annual surveillance
• Discharge at 3–5 years if no recurrence
• No systemic metastatic risk - no chest imaging required
• Patient education: advise that multiple local excisions may be necessary
• Red flags: rapid regrowth at excision site, new mass within months of surgery
• High recurrence rate after excision; active surveillance required