Figure 1. A typical epidermal cyst exhibiting granular cell layer and keratinisation (a and b: arrows). Malignant transformation into an acantholytic squamous cell carcinoma, without any dysplastic changes of the epithelium of the epidermal cyst (a and b: arrowheads) (Haematoxylin and eosin stained sections, x 100). Tumour cells showing nuclear polymorphism with hyperchromatism and keratinisation, loss of cellular cohesion and frequent mitoses (c and d: arrows) (Haematoxylin and eosin stained sections, c: x 200 and d: x 400).