Ultrastructural and morphological analysis during progression of Bowen disease reveals a complex interplay between hyperkeratosis, cytokeratin expression, host immunity and amyloid deposition

Background Bowen disease, one of the common skin cancers, is defined as squamous cell carcinoma in situ , characterized by atypical keratinocytes occupying the full thickness of the epidermis, and predominantly occurs on sun-protected skin. There is no existing data on the impact of tumour and immune cell interactions or cytokeratin expression on the pathology of Bowen disease. Objectives We analysed dynamic changes in cytokeratin expression and immune cell composition during the development and progression of Bowen disease. Materials & Methods Analysis was performed using immunohistochemistry and electron microscopy for samples from 140 patients with Bowen disease and 20 patients with invasive squamous cell carcinoma. We evaluated cytokeratin expression, the number of infiltrating immune cells and amyloid deposition by immunohistochemistry, and the ultrastructural relationship between tumour cells and immune cells by electron microscopy. Results The results showed that the expression of CK14 is associated with tumour progression, keratotic status and amyloid deposition and that the expression of CK10 is associated with accumulation of immune cells in Bowen disease. The findings of electron microscopy indicated repeated battles involving immune cells in response to tumour invasion. Conclusion The expression of cytokeratins, hyperkeratosis, inflammatory infiltration and amyloid deposition are useful findings indicating the “stage” in Bowen disease.