title: Anaplastic large cell lymphoma presenting as a pleural effusion and mimicking primary effusion lymphoma. A report of 2 cases.
abstract: BACKGROUND
  Systemic anaplastic large cell lymphoma (ALCL) is predominantly a nodal disease, but extranodal involvement can occur during the disease course or as the primary presentation. We report two rare cases of ALCL presenting with a pleural effusion, mimicking primary effusion lymphoma (PEL).
  
  
  METHODS
  Two patients, a 47-year-old woman and an 81-year-old man, presented with a pleural effusion for investigation. The pleural fluid contained abundant, large, lymphoid cells with marked nuclear atypia. These neoplastic cells strongly expressed CD30 and EMA and showed a T-cell phenotype (CD3+CD45RO+ for case 1 and CD4+ for case 2). Case 1, in addition, showed ALK1 expression. The tumor cells in both cases were negative for human herpes virus type 8 (HHV8) and Epstein-Barr virus (EBV). ALCL shows overlapping cytologic features with PEL, but the T-cell phenotype, ALK1 expression in case 1, lack of association with HHV8 and EBV, HIV seronegativity and subsequent discovery of nodal disease in case 2 were all in favor of ALCL over PEL.
  
  
  CONCLUSIONS
  In rare cases a pleural effusion is the presenting feature of ALCL, and distinction from PEL depends on correlation with clinical findings, detailed immunophenotyping and study of the status of HHV8 and EBV.
authors.affiliation: Department of Pathology, Queen Elizabeth Hospital, 30 Gascoigne Road, Kowloon, Hong Kong. chancl@ha.org.hk
authors.forename: Alexander Chak-Lam
authors.initials: AC
authors.lastname: Chan
authors.forename: John Kwok-Cheung
authors.initials: JK
authors.lastname: Chan
authors.forename: Kin Wing
authors.initials: KW
authors.lastname: Yan
authors.forename: Yok Lam
authors.initials: YL
authors.lastname: Kwong
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000077548:Anaplastic Lymphoma Kinase; D015703:Antigens, CD / Q000378:metabolism; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007124:Immunoenzyme Techniques; D016130:Immunophenotyping; D017728:Lymphoma, Large-Cell, Anaplastic / Q000175:diagnosis* / Q000201:enzymology; D008297:Male; D008875:Middle Aged; D016066:Pleural Effusion, Malignant / Q000175:diagnosis* / Q000201:enzymology; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D020794:Receptor Protein-Tyrosine Kinases
chemical_list: D015703:Antigens, CD; D000077548:Anaplastic Lymphoma Kinase; D011505:Protein-Tyrosine Kinases; D020794:Receptor Protein-Tyrosine Kinases