A male patient presents with elevated Beta-hCG and constant facial flushing. What is the most likely diagnosis?

The presentation of elevated Beta-hCG (human chorionic gonadotropin) associated with constant facial flushing is highly suggestive of choriocarcinoma. Choriocarcinoma is a type of germ cell tumor that can arise in the testes and is characterized by the production of Beta-hCG, which is a hormone typically produced during pregnancy.

In males, elevated levels of Beta-hCG can indicate the presence of a testicular germ cell tumor, and choriocarcinoma specifically is known for this feature. The constant facial flushing may be attributed to the paraneoplastic effects of the tumor, which can include various systemic symptoms due to hormone production or other biological effects of the cancer. This aligns with the nature of choriocarcinoma, where significant hormonal activity often manifests as systemic symptoms.

Other options present different types of tumors, which either do not typically produce Beta-hCG or have distinct clinical features that do not align with elevated levels of this hormone combined with facial flushing. Thus, the combination of elevated Beta-hCG and facial flushing strongly points toward choriocarcinoma as the most likely diagnosis.