Cell proliferation and p53 expression in pseudoepitheliomatous hyperplasia of oral paracoccidioidomycosis.

Paracoccidioidomycosis (PCMycosis) is a systemic mycosis frequently found in many regions of Latin America. Microscopically, it is characterised by granulomatous inflammation and pseudoepitheliomatous hyperplasia (PEH). This work describes the proliferation index and p53 expression by immunohistochemistry in PEH of PCMycosis, normal oral mucosa (NOM) and mild oral epithelial dysplasia (ED). Ki67 positive cells were present in the basal and parabasal layers in NOM and PEH, while in ED it was also observed in the spinous layer. Percentage of ki67 positive cells was 7.7, 28.2 and 46.0 in NOM, PEH and ED respectively. p53 was negative in NOM and in PEH it was expressed by few cells in the basal layer of only three cases. However, it was expressed in all cases of ED, in basal and parabasal layers. Although histologically PEH mimics well-differentiated squamous cell carcinoma, its proliferative pattern and p53 expression are more similar to NOM than to dysplasia. These findings, confirm PEH as a reactive process probably associated with the underlying chronic inflammation.