Signet-ring cell lymphoma in the orbit: a case report and review.

The authors report on the first case of signet-ring cell lymphoma involving the orbit. This variant of non-Hodgkin's lymphoma contains either vacuolated or eosinophilic cytoplasmic inclusions that squeeze the nucleus to one side of the cell. In this case, the inclusions were eosinophilic and stained positively for PAS, immunoglobulin M (IgM) heavy chain and kappa light chain. Electron microscopy showed granular electron-dense material trapped within distended loops of rough endoplasmic reticulum. Twenty-two cases of signet-ring cell lymphoma previously reported elsewhere in the body are reviewed, and their clinical significance is discussed.