The surface coat of the human effusion cells.

Cancer cells of human effusions have a prominent surface coat clearly demonstrated by ruthenium red staining. The cancer cells forming clumps are usually interconnected with each other by gap junctions which is expressed by a free penetration of the ruthenium red through the majority of the junctions. The benign cells encountered in human effusions are also covered with the surface coat, which, however, is usually thinner in comparison to the coat observed on the cancer cells.