Low-grade (fibromatosis-like) spindle cell tumour of the breast

At the low grade end of the spectrum of spindle cell carcinoma (metaplastic carcinoma) of the breast, there are tumours with mildly atypical features resembling fasciitis, fibromatosis or myofibroblastic tumours. However, these tumours have the potential for local and distant metastases and need to be differentiated from benign mimics.

Clinical features

This is a tumour of postmenopausal women.

Macroscopic appearances

The tumours are described as hard masses with a gritty grey-white cut surface.

Histopathology

These tumours are defined as consisting predominantly (>95%) of spindle cells. There is a fibromatosis-like growth pattern with finger-like projections extending into adjacent breast tissue. Cellularity and the amount of collagenous stroma varies. In some cases, there are foci of "epithelioid" cells which blend with the spindle cells. In other there are definite squamous or glandular foci.

Immunohistochemistry based on 24 cases1:

Differential diagnosis

• fibromatosis

• nodular fasciitis

• inflammatory myofibroblastic tumour (inflammatory pseudotumour)

• reactive spindle cell nodules (after biopsy): express only SMA and muscle-specific actin

• low-grade spindle cell sarcoma:

  • leiomyosarcoma shows greater reactivity for SMA and muscle-specific actin

  • MFH show more pleomorphism, may be focally positive for SMA

Prognosis

10 of the 34 patients with follow up showed local recurrence, in nine cases after local resection rather than wide excision or mastectomy. Two women who had had radical mastectomy developed lung metastases within two years and died of disease: these two patients had relatively large primary tumours (4.5 cm and 5 cm respectively).

References

1Sneige, N., Yaziji, H., Mandavilli, S. R. Low-grade (fibromatosis-like) spindle cell carcinoma of the breast. Am J Surg Pathol 2001;25:1009-1016.

This page last revised 24.12.2001.