KRT5 and carcinosarcoma: Immunofluorescence and immunohistochemical analysis of tumor sections revealed the presence of basal-like (K5/6 positive) and luminal-like (K8/18 positive) epithelial cells in fibroadenomas (Figure 6Ai) and carcinosarcomas (Figure 6Aii) while the squamous elements of the adenosquamous carcinomas (Figure 6Aiii) contained only K5/6 positive cells.