A case of swine follicular lymphoma with intracytoplasmic immunoglobulin inclusions.

A case of swine follicular lymphoma with Russell body-type inclusions is described in a 4-year-old pig. Distinct neoplastic follicles were observed in various lymph nodes and contained many cells with Russell body-type inclusions that were positive for IgM and corresponded to dilated cisternae of the RER. Desmosome-connected dendritic reticulum cells and neoplastic cells with desmosome-like structures demonstrated the germinal centre origin of this tumour. Although such cases have been reported in man, this is the first recorded case of swine follicular lymphoma showing this feature. The histological similarity of swine follicular lymphoma with Russell body-type inclusions to that of man is discussed, as is the relationship between reactive follicular hyperplasia and follicular lymphoma.