ALK and EGFR expression by immunohistochemistry are associated with Merkel cell polyomavirus status in Merkel cell carcinoma

Abstract

Aims

Merkel cell carcinoma, a rare cutaneous neuroendocrine tumor of the skin, can be categorized into two groups according to Merkel cell polyomavirus (MCV) presence. MCV‐negative tumors are more aggressive and frequently associated with gene mutations. Some of the genes are potential therapeutic targets. We have previously reported EGFR mutations in 6/27 MCC tumors and overexpression of ALK and EZH2 at mRNA level in MCC tumors. In this study, we sought to determine expression of ALK, EGFR and EZH2 in MCC samples and assess their correlation to MCV status and clinical parameters.

Methods and results

Tissue microarrays were utilized and stained with primary antibodies. Staining data was statistically compared to patient sex, tumor location and development of metastasis and MCC specific death. 112 tumors and their corresponding patient data were included. We found strong expression of ALK in 51% and strong expression of EZH2 in 76% of the tumors. There was evident correlation of ALK expression with MCV‐positivity. Expression of EGFR was infrequent presenting only in 7 MCV‐negative tumors. None of the proteins associated with development of metastasis or MCC specific death.

Conclusions

ALK and EZH2 expression are frequent in MCC and ALK expression correlates to MCV positivity. EGFR positive tumors might respond to EGFR inhibiting treatment.

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