[A case of a primary effusion lymphoma in the elderly].

We report a 90-year-old man who was given a diagnosis of pleural effusion lymphoma (PEL) based on the detailed immunochemical and DNA analyses of the pleural effusion. He was bed-ridden and on enteral nutrition due to severe Alzheimer's disease, and also had diabetes mellitus. He was transferred to our hospital with fever and massive pleural effusion. A cytological examination of the pleural effusion revealed class 5 atypical lymphocytes with a high nucleus/cytoplasm ratio. The origin of the atypical cells could not be determined by flow cytometry of the pleural effusion, which only suggested the existence of inflammatory changes. Considering his general physical status, further investigations were not performed. The respiratory failure progressed, and he died on the 45(th) hospital day. At autopsy, no atypical cells were identified in his organs other than in the right thoracic space. We conducted immunochemical staining after making a cell block from the effusion sample. Most of the atypical cells were CD30 positive, with human herpes virus-8 (HHV-8)-associated protein. A PCR analysis of the immunoglobulin heavy chain gene detected monoclonal rearrangement, thus indicating the atypical cells to be involved in the B-cell lineage. These findings led to a final diagnosis of PEL. PEL is a rare type of lymphoma confined to the body cavities without any prominent tumor mass, and its pathogenesis is related to HHV-8 infection. PEL develops mostly in immunocompromised patients, such as those with AIDS. However, it may also occur in elderly patients as well. We should therefore also consider the possibility of PEL in elderly patients presenting with pleural effusion of unknown origin.