Aims: To study and compare the expression of p63 protein and smooth muscle actin in breast tubular carcinoma (TC) and its main differential diagnoses, radial scar (RS)/complex sclerosing lesion (CSL).
Materials and methods: Immunohistochemistry techniques were used to search for p63 protein and smooth muscle actin antibodies in 10 patients with TC and fifteen with RS/CSL.
Results: Myoepythelial cells were diffusely positive for both actin and p63 protein with a cytoplasmic (actin) or nuclear (p63) pattern in all patients with RS/CSL. Inversely, all TC were negative for p63. Actin antibodies failed to label myoepithelial cells in TC, but both vessels and stromal myoblasts were actin-positive, creating difficult interpretation situations. By contrast, p63 was consistently negative in these structures.
Conclusion: For the differential diagnosis between TG and CR/LSC, smooth muscle actin and p63 protein demonstrate equivalent sensitivity for the detection of myoepithelial cells. However, the nuclear pattern of p63 labeling gives a "cleaner" stain. In addition, p63 enables distinction between myoepithelial cells and myofibroblasts/vascular smooth muscle cells, offering increased specificity.