Expression of polo-like kinase (PLK1) in thin melanomas: a novel marker of metastatic disease.
BACKGROUND
The maximum thickness of a primary malignant melanoma as measured by Breslow's method is currently the most important prognostic factor. However, some thin melanomas (< or= 0.75 mm), which should have an excellent prognosis according to Breslow, can be lethal due to their ability to metastasize.


METHODS
In our study, thin malignant melanomas (< or= 0.75 mm) from 36 patients were analyzed with immunohistochemical techniques using monoclonal antibodies directed against PLK1 and Ki-67. The immunoreactivity of 22 melanomas which developed metastases within 5 years of follow-up was compared with a group of 14 non-metastasized melanomas. Two independent investigators evaluated stained sections. Differences of PLK1 and Ki-67 indices between melanomas with and without metastases were tested statistically using the Mann-Whitney U-test.


RESULTS
Malignant melanomas with metastases expressed PLK1 at markedly elevated levels compared to melanomas without metastases (median, 60.00% vs. 37.98%; p = 0.000053). The difference of the Ki-67 index between both groups was not significant (median, 6.35% vs. 4.53%; p = 0.150473).


CONCLUSIONS
Our results suggest that PLK1 expression in thin melanomas is a reliable marker to identify patients at high risk for metastases.
Department of Dermatology, Johann Wolfgang Goethe-University, School of Medicine, Theodor-Stern-Kai 7, 60590 Frankfurt, Germany.
Lucas
L
Kneisel
Klaus
K
Strebhardt
August
A
Bernd
Manfred
M
Wolter
Angelika
A
Binder
Roland
R
Kaufmann
D018797:Cell Cycle Proteins; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D019394:Ki-67 Antigen / Q000378:metabolism; D008297:Male; D008545:Melanoma / Q000201:enzymology* / Q000556:secondary / Q000601:surgery; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local; D011379:Prognosis; D011494:Protein Kinases / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D012878:Skin Neoplasms / Q000201:enzymology* / Q000473:pathology / Q000601:surgery; D000097869:Polo-Like Kinase 1
D018797:Cell Cycle Proteins; D019394:Ki-67 Antigen; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D000097869:Polo-Like Kinase 1