Proliferating trichilemmal tumour: p53 immunoreactivity in association with p27(Kip1) over-expression indicates a low-grade carcinoma profile

Aims: Alterations of cell-cycle regulatory molecules in tumorigenesis may p redict the biological behaviour of neoplasms and greatly contribute to thei r proper classification. Since the behaviour of proliferating trichilemmal tumour (PTT) is controversial, we decided to explore the possible significa nce of altered p53 and p27(Kip1) immunohistochemical expression patterns in PTT, Methods and results: We evaluated the percentage and distribution of positi ve tumour cells and compared the results with those obtained from usual tri chilemmal cysts (TC) and squamous cell carcinomas with trichilemmal differe ntiation (SCCT), PTT showed p53 immunoreactivity (50.4 +/- 29.6. mean +/- s tandard deviation) that was not statistically different from that seen in S CCT (75.2 +/- 36.3), On the other hand, p53 immunostaining was virtually ab sent in TC cases (positivity for p53 was observed in only one instance in < 1% of cells), As for p27(Kip1), the mean percentage of positive cells in P TT (82.7 <plus/minus> 9.9) was slightly lower than in TC (90.6 +/- 4.6) but significantly higher than in SCCT (53.4 +/- 30), Conclusions: The similar p53 immunoreactivity in both PTT and SCCT favour t he interpretation of the former as carcinoma, albeit one whose behaviour wo uld be tempered by the well-known regulatory effect exerted by p27(Kip1), t he cell cycle.