Synonyms

• AFH
• angiomatoid Malignant Fibrous histiocytoma

Category

Soft tissue

Behaviour

Intermediate

Gender

Both equally

Tissue of Origin

Fibrous

Epidemiology

• Rare intermediate-grade soft tissue tumour
• Peak incidence in children and young adults (1st–3rd decades)
• 0.3% of soft tissue tumours

Clinical Features

• Slow-growing subcutaneous nodule
• Often associated with systemic symptoms: fever, anaemia, weight loss (paraneoplastic)
• Occasionally pulsatile or fluctuant mass
• Rarely causes metastasis

Location

• Extremities (limbs) most common
• Trunk
• Head and neck region
• Subcutaneous or deep dermal location

Imaging

• Well-circumscribed heterogeneous mass on MRI
• Haemorrhagic cystic spaces on T2-weighted imaging
• Pseudoangiomatous spaces not truly Vascular
• CT: well-defined soft tissue mass

Pathology

• Multinodular Fibrous pseudocapsule with peripheral lymphoid cuff
• Pseudoangiomatous blood-filled spaces
• Spindle cell fascicles with histiocytic appearance
• EMA, desmin, CD99 positive; EWSR1 rearrangement

Genetics

• EWSR1-CREB1 fusion most common (75%)
• EWSR1-ATF1 fusion (18%)
• FUS-ATF1 fusion (rare)
• Molecular testing confirms diagnosis

Treatment

• Wide local excision with clear margins
• No standard systemic therapy for localised disease
• Systemic therapy considered for metastatic disease (rare)

Prognosis

• Excellent prognosis for localised disease
• Local recurrence 15%
• Metastasis rare (<5%)
• Overall survival >95%

Key Points

• Can mimic haematoma or cyst clinically and radiologically
• EWSR1 rearrangement is diagnostically useful
• Paraneoplastic symptoms resolve after excision
• Despite intermediate classification, behaves nearly Benign

Workup - Blood Tests

• FBC - anaemia if paraneoplastic Syndrome present
• ESR, CRP - may be elevated in paraneoplastic context
• U&E, LFTs - pre-operative baseline

Workup - Local Imaging

• Ultrasound
• MRI primary site

Workup - Biopsy

• Core needle biopsy or excision biopsy
• Immunohistochemistry: EMA+, desmin+, CD99+
• Molecular: EWSR1 FISH (rearrangement in 93%) - confirms diagnosis
• EWSR1-CREB1 fusion most common

Workup - Staging

CT chest - metastasis rare but should be excluded at staging

Workup - Other

MDT review with sarcoma specialist centre

Follow-up Summary

• Post-op visit within 6 weeks
• Year 1: Clinical review at 3 months (to assess function), then 6-monthly clinical exam + CXR
• Year 2: 6-monthly clinical exam + CXR
• Years 3+: Annual clinical exam + CXR
• Routine MRI of primary site not indicated unless difficult to assess clinically
• Paraneoplastic symptoms (fever, anaemia, weight loss) resolve post-excision - reassure patient