Myofibroblastic differentiation in malignant fibrous histiocytoma (pleomorphic myofibrosarcoma): a clinicopathological study.
OBJECTIVE
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.


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.
Montgomery
E
E
The Royal Marsden NHS Trust, London, UK. cfisher@icr.ac.uk
Fisher
C
C
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000951:Antigens, Neoplasm / Q000032:analysis; D014408:Biomarkers, Tumor / Q000032:analysis; D002454:Cell Differentiation; D002471:Cell Transformation, Neoplastic; D005260:Female; D005347:Fibroblasts / Q000737:chemistry / Q000648:ultrastructure; D019084:Fluorescent Antibody Technique, Indirect; D018219:Histiocytoma, Benign Fibrous / Q000737:chemistry / Q000401:mortality / Q000473:pathology*; D006801:Humans; D008297:Male; D008854:Microscopy, Electron; D008875:Middle Aged; D015388:Organelles / Q000648:ultrastructure; D012189:Retrospective Studies; D012983:Soft Tissue Neoplasms / Q000737:chemistry / Q000401:mortality / Q000473:pathology*; D015996:Survival Rate
D000951:Antigens, Neoplasm; D014408:Biomarkers, Tumor