Merkel cell polyomavirus
The MCV is a small double-stranded DNA virus that is believed to contribute to the development of the majority of MCC. About 80% of MCC tumors are infected with MCV, with the virus integrated into the host genome in a monoclonal pattern. However, the majority of people with MCV infection do not develop MCC: MCV is a ubiquitous virus and infection commonly occurs during childhood but remains asymptomatic throughout an individuals lifetime.MCC was first believed to be associated with MCV when it was observed to occur at a much higher rate in HIV patients during the 1980s. Since then, studies have demonstrated integration of the MCV genome into the genome of MCC tumor cells. Central to the our understanding of the pathogenicity of MCV are two viral proteins expressed in infected cells known as the large tumor antigen (LT) and small tumor antigen (sT). Normally, patients infected with MCV show low levels of antibodies to the LT protein, perhaps due to a nuclear localization domain in its C-terminal that limits its cellular dispersion. However, integration of the viral genome into the host genome can result in truncation of the LT protein proximal to this domain. This serves two oncogenic purposes: first, it prevents successful viral replication that would culminate in lysis of the infected cell. Second, it redistributes the LT protein to the cytoplasm, where it can interact with cytoplasmic signaling.
Cor bovinum  or cor bovis refers to a massive hypertrophy of the left ventricle of the heart due to volume overload, usually in earlier times in the context of tertiary syphilis but currently more often due to chronic aortic regurgitation, hypertensive and ischaemic heart disease. Pathophysiology
Due to Syphilitic aortitis (a complication of tertiary syphilis) the aortic valve ring becomes dilated. The free margins of valve cusps no longer approximate leading to aortic valve insufficiency. As blood regurgitates into the left ventricle between each systole, volume overload ensues and the ventricular wall hypertrophies in an attempt to maintain cardiac output and blood pressure. The massive ventricle can lead to a heart weighing over 1000 grams (the weight of a normal heart is about 350 grams), referred to as cor bovinum (Latin for cows heart).Fluri and Gebbers define cor bovinum as a heart exceeding 500 g in weight. Looking through autopsies on Internal Medicine patients at the Kantonsspital Luzern, they found 415 cases out of 1181 autopsies in the two periods 1978-81 and 1997-2000. Cor bovinum was found in 25.3% of cases in the earlier period, with mean age at death 67.7 years, and in the later period 20.6% with mean age 74.3 years. The male female ratio was 4:1. "In 93% of all patients with CB, we found coronary atherosclerosis as a sign of high blood pressure and in 79% a COPD."