title: Primary effusion lymphoma: a series of 4 cases and review of the literature with emphasis on cytomorphologic and immunocytochemical differential diagnosis.
abstract: BACKGROUND
  Primary effusion lymphoma (PEL) is a human herpes virus-8 (HHV-8)-associated and very rare type of lymphoma usually confined to the body cavities and commonly observed in human immunodeficiency virus (HIV)-infected patients. A comparison was made between the cytologic and immunocytochemical features of 4 cases of PEL encountered in the authors' department with those reported to date in the literature.
  
  
  METHODS
  A comprehensive comparison of the cytologic and immunocytochemical features of the 4 cases with those reported in the literature was conducted.
  
  
  RESULTS
  Cytologically, the most consistent features of the 4 cases and those in the literature included large cell size, moderate to abundant cytoplasm, a single nucleus in most cells with occasional bi- or multinucleated giant cells, single to multiple prominent nucleoli, and coarse chromatin. Immunocytochemically, only 2 (50%) of the current cases were of the null-phenotype compared with 93% of cases in the literature; the other 2 cases had a T-cell phenotype. Activation markers were expressed in 50% and 78% of the current cases and the literature cases, respectively. Positivity for HHV-8 was proven in the 4 cases by immunocytochemistry.
  
  
  CONCLUSIONS
  Cytomorphologically, PEL exhibits features bridging large cell immunoblastic and anaplastic large cell lymphoma. Although it is usually of null-phenotype, it may occasionally express B-cell or T-cell markers, rendering its distinction difficult from other lymphomatous effusions on a cytologic and immunocytochemical basis alone. Therefore, HHV-8 detection is an essential confirmatory ancillary test in suspected cases of PEL.
authors.affiliation: Department of Pathology, McGill University and McGill University Health Center, Montreal, Quebec, Canada.
authors.forename: Fadi
authors.initials: F
authors.lastname: Brimo
authors.forename: René P
authors.initials: RP
authors.lastname: Michel
authors.forename: Karim
authors.initials: K
authors.lastname: Khetani
authors.forename: Manon
authors.initials: M
authors.lastname: Auger
mesh_terms: D000328:Adult; D006566:Herpesviridae Infections / Q000175:diagnosis* / Q000473:pathology*; D019288:Herpesvirus 8, Human / Q000302:isolation & purification*; D006801:Humans; D016483:Lymphoma, AIDS-Related / Q000175:diagnosis; D016403:Lymphoma, Large B-Cell, Diffuse / Q000473:pathology / Q000821:virology; D008228:Lymphoma, Non-Hodgkin / Q000175:diagnosis* / Q000473:pathology* / Q000821:virology; D008297:Male; D016066:Pleural Effusion, Malignant / Q000175:diagnosis* / Q000473:pathology*