Spindle cell carcinoma of the breast: A case report and an immunohistochemical study including p53 and Ki‐67 expression

A rare case of spindle cell carcinoma (SpCC) of the breast occurring In a 51-yearold Japanese woman Is reported. A firm and well-circumscribed tumor, measuring 9times8.5times8.5 cm, was located on the upper lateral region of the right breast. Microscopically, the tumor consisted of sheets of both malignant spindle cells and poorly differentiated ductal carcinoma containing squamold islands with gradual transition to the spindle cell component. The Immunocyto chemical expression of epithelial markers was recognized in the spindle cells, as well as in the carcinomatous cells. Moreover, the spindle cell component expressed vimentin, α-smooth muscle actln and S-100 protein. Ultrastructurally, in addition to the features of adenocarcinoma, squamous or rnyoeptthelial differentiation was confirmed in the spindle cell component. These findings thus suggest an epithelial origin with squamous differentiations and myoepithellal participation In the genesis of SpCC. In a comparative study, the expression of p53 protein and KI-67 as a proliferation marker In each component of this tumor was also Investigated. The mean p53 labeling index (LI) in both the carcinomatous and spindle cell area was similar, however the mean MIB-1 LI in the spindle cell area was significantly higher than that in the carcinomatous area. The results indicate that p53 over-expression is Involved In the tumorigenesis of both components in the SpCC, and the spindle cell component shows a higher degree of proliferative activity than the carcinomatous component.