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solitary fibrous tumor; fibrous mesothelioma; pleural fibroma
originally described as a mesenchymal pleural tumor; can occur at many different sites.
Microscopic Pathology:
- patternless architecture
- alternating hypo- & hypercellular areas separated by thick bands of hyalinized collagen and branching vessels
- round to spindle shaped cells
- little cytoplasm
- indistinct borders
- vesicular nuclei
- myxoid areas, fibrosis common
- mitoses scarce, rarely > 3 per 10 HPF malignant solitary fibrous tumor:
- hypercellular
- at least focal moderate to marked cytologic atypia
- tumor necrosis
- numerous mitoses (> 4 per HPF)
- infiltrative margins
Immunohistochemistry:
- CD34 + (~90-95%)
- CD99 + (70%)
- bcl-2 variable + (~20-35%)
- EMA variable + (~20-35%)
- vimentin +
- cytokeratin usually -
- CD31 -
- actin -
Clinical manifestations:
- well delineated, slow growing, painless mass
- compression symptoms if large (nasal cavity, orbit or meninges)
- most cases benign
- ~10-15% behave aggressively (not strict correlation between morphology and behavior although most can be predicted by histology)
- tumors in mediastinum, abdomen, pelvis and retroperitoneum tend to be more aggressive than in extremities
- metastases to bone, liver, lung
General
intermediate grade fibroblastic/myofibroblastic neoplasm
References
- Dabbs. Diagnostic Immunohistochemistry. Churchill-Livingstone,
2002.
- WHO Classification Tumours of Soft Tissue and Bone
Fletcher, Unni & Mertens Eds. IARC Press 2002
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