Expression of erythropoietin receptor in human Merkel cell carcinoma of the eyelid.

BACKGROUND Merkel cell carcinoma (MCC) of the eyelid is a rare malignant solid tumor of the elderly, which demonstrates a large, firm, reddish nodule mimicking an angiomatous lesion. The expression of erythropoietin (Epo) and Epo receptor (EpoR), as well as vascular endothelial growth factor (VEGF), VEGF receptor (VEGFR) and basic fibroblast growth factor (bFGF) were examined in human MCC tissues. MATERIALS AND METHODS Three patients diagnosed with MCC of the eyelid underwent surgical excision. Isolated tissues were fixed by 4% paraformaldehyde and then were examined using immunohistochemistry. RESULTS The carcinoma cells consisted of irregular tumor nests with linear stroma and showed hypercellularity indicated by small round nuclei with several mitoses. While immunoreactivity of Epo was undetectable, an increased expression of EpoR was noted in the carcinoma cells. Cytoplasmic immunoreactivity for EpoR was detected in a variety of carcinoma cells, including mitotic cells. VEGF, VEGFR, and bFGF, other angiogenic factors were not expressed in the MCC tissues. CONCLUSION EpoR was highly expressed in MCC of the eyelid, suggesting that the Epo-EpoR pathway plays an important role in the formation of MCC.