[Metaplastic spindle-cell (fibromatosis-like) carcinoma of the breast--report of 4 cases].

The authors report about clinico-morphological features in four cases of spindle-cell metaplastic carcinoma of the breast, closely mimicking benign soft tissue fibromatosis or nodular fasciitis. All patients were females aged 54-72 years with a palpable nodule within the breast, 20-35 mm in size. Histologically, the tumor infiltrated surrounding tissue; it consisted of spindle cells with relatively bland morphology, arranged in a fascicular, storiform or random fashion. Mitotic activity was low, focally the tumors revealed regressive changes (hyalinization, myxoid degeneration). Cytokeratin expression was proven in all four cases. In two patients the tumor metastasized and the patients died of it; this fact confirms recently published data that despite its deceptively benign appearance, fibromatosis--like carcinoma of the breast is undoubtedly a malignant process with potentially aggressive behaviour. Differential diagnosis of this unusual variant of metaplastic breast carcinoma is discussed together with related therapeutic issues.