Myofibroblastic differentiation in malignant fibrous histiocytoma (pleomorphic myofibrosarcoma): A clinicopathological study

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Aims: We compared the clinical and pathological features of pleomorphic malignant fibrous histiocytoma (MFH)-like soft tissue sarcomas with and without myofibroblastic differentiation on electron microscopy. Methods and Results: Fifty-three soft tissue tumours designated as MFH by light and electron microscopy were reassessed. Eighteen were specifically diagnosed and excluded, and follow-up (FU) information obtained for 24 of the other 35 cases. Myofibroblastic ultrastructure was seen in 7/24 (29%). Seventeen of 24 (71%) lacked myofibroblasts on electron microscopy, which showed fibroblastic or undifferentiated cells. Histologically, all tumours but one had storiform-pleomorphic areas: one myofibroblastic neoplasm was fascicular and myxoid. No other morphological differences were seen. In seven myofibroblastic cases, smooth muscle in four cases and muscle-specific actin in two cases, desmin in three cases and S100 in one case were present. In 15 other tumours, smooth muscle in five cases and muscle-specific actin in one case, and desmin in one case were present; none of these cases expressed S100. CD34 was found in the myxoid areas of one myofibrosarcoma and 3/15 other tumours. Positivity for bcl-2 was seen only in non-myofibroblastic sarcomas (4/14). On follow-up (median 41 months), 2/7 (29%) myofibroblastic tumours recurred, 5/7 (71%) metastasized, and 3/7 (43%) patients died of disease. Among the non-myofibroblastic sarcomas, with a median follow-up of 47 months, 6/17 cases (35%) recurred, 10/17 (59%) metastasized, and 7/17 patients (41%) died of disease. Conclusions: Pleomorphic sarcomas with and without myofibroblastic differentiation on electron microscopy are clinically and histologically similar. The former display myoid immunohistochemical markers more frequently.

Original languageEnglish (US)
Pages (from-to)499-509
Number of pages11
Issue number6
Publication statusPublished - 2001
Externally publishedYes



  • Electron microscopy
  • Fibrosarcoma
  • Malignant fibrous histiocytoma
  • Myofibroblastic sarcoma
  • Myofibroblasts
  • Pleomorphic sarcoma
  • Sarcoma

ASJC Scopus subject areas

  • Anatomy
  • Pathology and Forensic Medicine
  • Cell Biology

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