Extracavitary Primary Effusion Lymphoma With an Atypical Immunophenotype. (21st September 2018)

• Record Type: Journal Article
• Authors: Penning, Alyssa; Cascio, Michael; Fan, Guang; Dunlap, Jennifer; Raess, Philipp
• Is Part Of: American journal of clinical pathology. Volume 150(2018)Supplement 1
• Page Start: S99
• Page End: S100
• Publication Date: 2018-09-21
• Subjects: Diagnosis, Laboratory -- Periodicals; Pathology -- Periodicals; 616.07
• DOI: 10.1093/ajcp/aqy097.240
• Languages: English
• ISSNs: 0002-9173

Abstract

Abstract: Immunodeficiency-related and virally mediated lymphoproliferative disorders can pose diagnostic challenges, especially when immunophenotypic findings are not typical. A 52-year-old male recently diagnosed with HIV/AIDS presented with a 2-month history of B symptoms, diffuse lymphadenopathy, and hepatosplenomegaly. The patient was adherent to antiretroviral therapy with a CD4 count of 110 and a low viral load. Excisional biopsy of a supraclavicular lymph node demonstrated partially preserved architecture with an interfollicular proliferation of medium to large plasmablastic cells with irregular nuclei, coarse clumped chromatin, prominent nucleoli, and brisk mitotic activity. A subset of residual follicles showed involvement by the population, and some showed regressive changes reminiscent of Castleman disease. Immunohistochemical analysis demonstrated CD45, MUM1, and C-MYC positivity; a Ki-67 proliferative rate of >95%; and weak/variable staining for CD20, CD79a, and CD19. The neoplastic cells were negative for CD5, CD10, PAX5, CD138, CD30, EMA, BCL2, and BCL6. HHV8 immunohistochemistry and EBV mRNA in situ hybridization were positive. Flow cytometry demonstrated a population with dim CD20 and bright CD38 and CD56 expression without surface or cytoplasmic light chain expression. A diagnosis of extracavitary primary effusion lymphoma (EC-PEL) was rendered. This entity is a rare HHV8-associated lymphoma that presents with nodal or solid organ involvement by a plasmablastic population of neoplastic cells. EC-PEL is typically HHV8/EBV positive and expresses markers of terminal B-cell differentiation (MUM1 and CD138) but shows weak expression of B-cell lineage markers and immunoglobulins. The current case shows an unusual lack of CD138, CD30, and EMA expression. Other entities considered in this differential included HHV8+ diffuse large B-cell lymphoma, HHV8+ germinotropic lymphoproliferative disorder, and HHV8+ multicentric Castleman disease. Accurate diagnosis of EC-PEL relies on integrating morphologic, immunophenotypic, and clinical findings. This case emphasizes the need for consideration of HHV8-associated lymphoproliferative disorders when evaluating specimens from patients with a history of immunodeficiency.