Bowen's1 "precancerous dermatosis" is still considered by some authors as a precancerous dyskeratotic process but is regarded by the majority as a highly specialized form of superficial squamous cell epithelioma with lateral intraepithelial spread.
The histologic characteristics of Bowen's disease of the skin were stated by Stout2 as follows:
The epidermal layer is thickened and sometimes made papillary by a multiplication and disorientation of the Malpighian cells. The cells vary in size and shape, there are many mitoses, and some of them are... abnormal. Monster cells with several nuclei centrally clumped together were originally described by Bowen.
Darier3 coined the term poikilokarynosis to describe these changes. Furthermore, foam cells (Kreibich4) with vacuolated cytoplasm, isolated cell nests within the epithelium (Grzybowski5) and cells with a clear vacuole partly or completely surrounding the nucleus (corps ronds, Darier) are sometimes observed. Intracellular fibrils are usually lost, but intercellular