Bcl-2 expression indicates better prognosis of Merkel cell carcinoma regardless of the presence of Merkel cell polyomavirus.

Merkel cell carcinoma (MCC) is an aggressive dermal tumour of neuroendocrine origin. The recently found Merkel cell polyomavirus (MCV) integrates clonally in the tumour genome, which suggests an important role in the pathogenesis of the disease. Previous small-scale studies have detected anti-apoptotic protein bcl-2 in 80 % of MCC tumours, but its correlation to the prognosis of MCC remains controversial. Our aim was to clarify the correlation of immunohistochemical expression of bcl-2 to MCV presence and MCC prognosis. We analyzed 116 primary MCC specimens with corresponding clinical data by immunohistochemistry for bcl-2. The presence of MCV DNA had been analyzed by quantitative PCR for 108 tumours. The correlations were analyzed statistically. Of the primary MCC samples, 85 % were bcl-2 positive. No significant differences in MCV DNA occurred between the bcl-2-positive and bcl-2-negative tumours. Local and systemic metastasis was more common in patients with bcl-2 negative tumours (33 %) than in patients with bcl-2-positive tumours (12 %; p = 0.04) at the time of diagnosis. The mean overall survival was higher in patients with bcl-2-positive tumours than of those with negative tumours (mean survival 1,814 days (5.0 years) vs. 769 days (2.1 years), p = 0.01). Bcl-2 positivity indicates better clinical stage at the time of diagnosis and a longer survival in MCC.