Metaplastic carcinomas of the breast. II. Spindle cell carcinoma.

The clinical and pathologic features of 100 examples of spindle cell carcinoma (SpCC) of the breast are reported. Eighty-three neoplasms contained overt carcinoma; 72 had infiltrating ductal or intraductal carcinoma and in 11 the carcinomatous component was purely squamous. Seventeen neoplasms lacked overt carcinoma, but were identified as SpCC by immunoreactivity for keratin and the typical bland spindle cell proliferation forming a variable complex of fibrocollagenous stroma with feathered, myxoid, angioid, and storiform patterns. Areas of epithelium merging imperceptibly with the spindle cell component were commonly observed. Sixty neoplasms were studied by immunohistochemistry for the presence of keratin, epithelial membrane antigen (EMA), vimentin, S-100, and actin. The spindle cell component in 98% of SpCC was immunoreactive for keratin. Most were also immunoreactive for vimentin and actin, and in approximately one half, S-100 immunoreactivity was noted. These findings, in conjunction with histopathologic features, and ultrastructural observations from three cases, support myoepithelium as an integral component of SpCC. The cumulative 5-year survival rate for SpCC was 64%, better than survival rates usually reported for metaplastic carcinomas. Of 47 patients with axillary dissection, only 6% had metastases to axillary lymph nodes. Development of metastasis was an ominous sign as 29 of the 30 patients who developed metastases died from tumor. Local recurrence was not as ominous as only 29% who had only local recurrence subsequently died from tumor. The difference in size between tumors that recurred (mean, 5.0 cm) and those that did not (mean 3.7 cm), and the presence or absence of complete microscopic circumscription, were both significant prognostic factors.