Proliferating trichilemmal tumour: p53 immunoreactivity in association with p27Kip1 over-expression indicates a low-grade carcinoma profile.
OBJECTIVE
Alterations of cell-cycle regulatory molecules in tumorigenesis may predict the biological behaviour of neoplasms and greatly contribute to their proper classification. Since the behaviour of proliferating trichilemmal tumour (PTT) is controversial, we decided to explore the possible significance of altered p53 and p27Kip1 immunohistochemical expression patterns in PTT.


RESULTS
We evaluated the percentage and distribution of positive tumour cells and compared the results with those obtained from usual trichilemmal cysts (TC) and squamous cell carcinomas with trichilemmal differentiation (SCCT). PTT showed p53 immunoreactivity (50.4 +/- 29.6, mean +/- standard deviation) that was not statistically different from that seen in SCCT (75.2 +/- 36.3). On the other hand, p53 immunostaining was virtually absent in TC cases (positivity for p53 was observed in only one instance in < 1% of cells). As for p27Kip1, the mean percentage of positive cells in PTT (82.7 +/- 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 the interpretation of the former as carcinoma, albeit one whose behaviour would be tempered by the well-known regulatory effect exerted by p27Kip1 on the cell cycle.
Fernández-Figueras
M T
MT
Department of Pathology, Hospital Universitari Germans Trias i Pujol, Carretera del Canyet s/n, 08916 Badalona, Spain. mtferfig@ns.hugtip.scs.es
Casalots
A
A
Puig
L
L
Llatjós
R
R
Ferrándiz
C
C
Ariza
A
A
D002294:Carcinoma, Squamous Cell / Q000378:metabolism / Q000473:pathology; D018797:Cell Cycle Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27; D006801:Humans; D007150:Immunohistochemistry; D008869:Microtubule-Associated Proteins / Q000032:analysis; D012878:Skin Neoplasms / Q000378:metabolism / Q000473:pathology*; D016159:Tumor Suppressor Protein p53 / Q000032:analysis; D025521:Tumor Suppressor Proteins
D018797:Cell Cycle Proteins; D008869:Microtubule-Associated Proteins; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27