Pathological analysis of MV-injected tumors shows the characteristic cytopathic effect of MV as demonstrated by anti–MV H staining, in situ hybridization for MV mRNA, and X-gal staining.

Replicating MV can be rescued from tumors up to 20 days after the final injection. (A) Hematoxylin and eosin staining of a section of Raji tumor showing multiple multinucleated syncytia. (B-C) Consecutive tissue sections stained with hematoxylin and eosin and with an anti–MV H antibody. Anti–MV H staining, which appears as brown staining upon a background of blue counterstain, is coincident with the MV-induced cytopathic effect. (D-E) Consecutive tissue sections stained with hematoxylin and eosin and subjected to in situ hybridization for MV N-specific mRNA. MV N mRNA appears as a dark brown–stained region upon a background counterstained pink with eosin. (F) Macroscopic X-gal–stained DoHH2 tumors injected with MVlacZ or control UV-inactivated MVlacZ. (G) A section from a DoHH2 tumor injected with MVlacZ and stained with X-gal. (H) X-gal–stained Vero cells 24 hours after coculture with a small tumor section. Large β-galactosidase–expressing syncytia are seen, a result of infection with replicating MVlacZ recovered from the tumor.