Pleomorphic leiomyosarcoma

Pleomorphic leiomyosarcoma is defined as a sarcoma showing typical leiomyosarcomatous fascicles but in which more than two thirds of the tumour is of pleomorphic morphology. Pleomorphic leiomyosarcoma differs from ordinary leiomyosarcoma in its morphology, reduced immunoreactivity for muscle markers, increased proliferative activity and more aggressive behavior. Pleomorphic leiomyosarcoma accounts for about 9% of all leiomyosarcomas.

Clinical features

Pleomorphic leiomyosarcoma tends to occur in middle aged to elderly adults, particularly in the extremities and retroperitoneum.

Histopathology

In most (23 of 28¹) cases, the pleomorphic areas blend with the leiomyosarcomatous fascicular areas.

Immunohistochemistry (with ordinary leiomyosarcomas and MFH for comparison):

	pleomorphic leiomyosarcoma		ordinary leiomyosarcoma	storiform-pleomorphic MFH
	fascicular areas	pleomorphic areas
desmin	18/281	10/281, 3/62	15/201	3/161 focally positive (less than 5% of the tumour cells)
muscle actin (HHF-35)	26/281	13/281, 2/62	14/201	1/161 focally positive (less than 5% of the tumour cells)
SMA	24/281	14/281	15/201	1/161 focally positive (less than 5% of the tumour cells)
calponin	20/281	16/281	18/201	2/161 focally positive (less than 5% of the tumour cells)
h-caldesmon	11/281	5/281	11/201	0/161 focally positive (less than 5% of the tumour cells)
Myo-D1	0/5 (these five cases showed rhabdoid features)1	0/5 (these five cases showed rhabdoid features)1
myogenin	0/5 (these five cases showed rhabdoid features)1	0/5 (these five cases showed rhabdoid features)1
p53 staining more than 10% of nuclei	8/281		5/201	5/161
murine double-minute 2	15/281		8/201	6/161
average MIB-1 labelling index	26.11	26.21	12.91	16.61

Cases with prominent osteoclast-like giant cells were excluded from this study¹.

Differential diagnosis

Among sarcomas, prominent pleomorphism is seen in pleomorphic sarcoma NOS (storiform-pleomorphic MFH), pleomorphic liposarcoma and pleomorphic rhabdomyosarcoma.

Prognosis

Of 22 with a significant period of follow up, 15 died of disease¹.

References

¹ Oda, Y., Miyajima, K., Kawaguchi, K.et al. Pleomorphic leiomyosarcoma: clinicopathologic and immunohistochemical study with special emphasis on its distinction from ordinary leiomyosarcoma and malignant fibrous histiocytoma. Am J Surg Pathol 2001; 25:1030-1038.

² Hashimoto, H., Daimaru, Y., Tsuneyoshi, M., Enjoji, M. Soft tissue sarcoma with additional anaplastic components. A clinicopathologic and immunohistochemical study of 27 cases. Cancer 1990;66:1578-1589.

This page last revised 26.12.2001.