malignant fibrous histiocytoma

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