Do measles early giant cells result from fusion of non-infected cells? An immunohistochemical and in situ hybridization study in a case of morbillous appendicitis.

A case of acute appendicitis with features of measles inflammatory reaction is studied. Two types of lymphoid polykaryons are seen: Warthin Finkeldey cells inside germinal centres (LN1 ++, LN2 +, L26 +, MB1 +, MB2 +/-) and multinucleate plasma cells in the lamina propria (mu +, alpha ++, kappa +, lambda +). Both types of polykaryon are devoid of inclusions. The search for viral genetic information by in situ hybridization was negative in these cells. A positive signal was observed in interfollicular mononuclear cells and rare enterocytes. A possible mechanism of fusion from without, acting at the beginning of the disease to induce the appearance of polykaryons, is discussed.