malignant fibrous histiocytoma

high power H&E stained section with malignant fibrous histiocytoma
HISTOPATHOLOGY
A now invalid waste-paper basket term for a group of malignant soft tissue tumours that were clinically characterised as pleomorphic mesenchymal neoplasms of older adults, affected deep soft tissues, involving muscle 60% or fascia 20% of the lower–50% and upper–20% extremities, retroperitoneum-15% and abdominal cavity, and histologically characterised as mitotically active spindled cells arranged in a storiform pattern. MFH is no longer considered an entity a sui generis, given that many MFHs proved to be melanomas, poorly-differentiated carcinomas and lymphomas, when examined by immunohistochemistry
Metastasis To lung 80%, lymph nodes 30%, liver, bone
Differential diagnosis Other sarcomas, pleomorphic carcinoma, anaplastic carcinoma, bizarre melanoma
Reclassification of MFH types
• Angiomatoid MFH, now Angiomatoid fibrous histiocytoma
• Inflammatory MFH, now Inflammatory de-differentiated liposarcoma
• Giant cell MFH, high grade, now Giant cell-rich extraskeletal osteosarcoma
• Giant cell MFH, low grade, now Giant cell tumour of soft tissue
• Myxoid MFH, now Myxofibrosarcoma
Prognosis 40-65% of tumours recur; 25-50% metastasise, 35-60% 5-year survival
Note: Conoscenti roll their eyes at the continued use of the short form–MFH and the long form–malignant fibrous histiocytoma, given that MFH was renamed pleomorphic undifferentiated sarcoma–PUS or undifferentiated pleomorphic sarcoma–UPS ages ago
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