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Peripheral T cell lymphoma, NOS with CD38 expression and downregulation of T cell markers

Background: Peripheral T cell lymphoma (PTCL), NOS is heterogeneous category of nodal and extranodal mature T cell lymphoma and it accounts for 30% PTCLs in western countries. Its aberrant expression of B lineage markers can sometimes be very misleading especially in the setting of profound downregulation of T cell markers. Principals/Methodology: To describe a case of PTCL, NOS with down expression of T cell markers and aberrant expression of CD38. Results: A 66-year old woman presented with generalized lymphadenopathy, weight loss and left leg lymph-edema, one month in duration. Cytological examination of the enlarged cervical lymph node aspirate revealed lymphatic cells at different stages of transformation with some epithelioid cells. Conglomerate of enlarged right axillary lymph nodes measuring 3.6x2.6x2 cm was examined. Standard H&E and Giemsa staining showed obliterated lymph node architecture, interfollicular infiltration of polymorphic medium to large sized atypical lymphatic cells some with blastoid and plasmablastic morphology with numerous mitoses and apoptosis. Also there was lots of accompanying plasma cells, eosinophils, and histiocytes. By immunohistochemistry large atypical lymphoid cells were CD38+, CD138-, CD30-/+, MUM1+, PD-1-/+, CD20-, CD79a+/-, PAX-5-, CD3-, CD5-, CD4-/+, CD2-, CD8-, Bcl-2-, Bcl-6-, CD10-, HHV-8- and EBER in situ negative. CD68 staining showed lots of histiocytes and Ki-67 was around 50%. Therefore, initial provisional differential diagnosis was DLBCL. PCR of immunoglobulin heavy chain in FR2A and FR3A regions showed polyclonal distribution, while T cell receptor analysis of TCR gamma region showed bi-clonal and TCR beta region monoclonal distribution. It is only after additional molecular analysis of clonality that diagnosis of PTCL-NOS was made. Conclusion: PTCL, NOS with aberrant B lineage expression and down regulation of T cell markers represents a diagnostic challenge and PCR clonality analysis is crucial for accurate diagnosis.

Aberrant expression ; Immunohistochemistry ; Clonality ; T lymphoma

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