Figure 5.

C4.4A, CK1 and CK14 expression signatures in proliferating invasive keratoacanthoma. Paraffin-embedded serial tissue sections were incubated with primary antibodies against C4.4A (A–C), CK1 (D–F) and CK14 (G–I) and stained using immunoperoxidase and NovaRED. The low magnification pictures in panels A, D, and G show an example of a whole keratoacanthoma, where weakened expression in the lesion center (A, C4.4A; G, CK14) or complete loss of expression (D, CK1) can be appreciated. Panels B, E, and F show high magnifications of the invasive fronts, with high C4.4A and CK14 expression and a lack of CK1 expression. C4.4A- and CK14-positive and CK1-negative perineural infiltrations are shown in (C), (F) and (I), respectively. Note the similarity in expression pattern of the three proteins in invasive squamous cell carcinoma and the invasive front of proliferating keratoacanthoma. Scale (A–C), 400 µm; (D–F), 100 µm; (G–I), 50 µm.