A koilocyte is a squamous epithelial cell that has undergone structural changes as a result of infection by human papillomavirus (HPV). This image of a koilocyte shows human ectocervical cells (HEC) expressing HPV-16 E5 oncoprotein, and immortalized with HPV-16 E6 and E7 oncoproteins. Formation of koilocytes requires cooperation between HPV E5 and E6 oncoproteins. The cell culture is stained with hematoxylin and eosin (H&E).

FREDERICK, Md. -- A new chemical test available through the Frederick National Laboratory for Cancer Research could accelerate human papillomavirus (HPV) research by detecting 40 percent more HPVs than the current gold standard research test. 

There are upwards of 100 human papillomaviruses (HPVs), and these viruses can cause abnormal tissue growth and other changes to cells. Prolonged infection with certain types of HPV can cause cancer.