This is an uncommon case of a peripheral T cell lymphoma, not otherwise specified (PTCL-NOS) containing Reed–Sternberg (R–S) like cells expressing CD15 and CD30. The lymph node is effaced by a polymorphous population of small, intermediate, and large lymphocytes amidst a background of histiocytes, plasma cells, and abundant eosinophils (Image 1). Sclerosis is also present, producing a nodular pattern (Image 1B). Among the large cells are multi-nucleate cells with Reed–Sternberg like cytology (Image 1A inset). The panel of immunostains performed included CD3, CD4, CD5, CD8, CD15, CD20, CD30, CD43, CD45, ALK1, and PAX5. The intermediate and large lymphocytes are positive for CD30 (Image 1C) and CD43 (Image 1E). Rare large R–S like cells also coexpress CD15 (Image 1D). PCR analysis detected a clonal gamma T cell receptor gene rearrangement.
Cases of PTCL-NOS containing R–S like cells expressing CD15 and CD30 have been reported [1–3]. Distinction from Hodgkin lymphoma requires careful assessment of morphology and immunophenotype, and is assisted by gene rearrangement analysis. Classical Hodgkin lymphoma is characterized by classic R–S cells and variants in a background of reactive eosinophils, plasma cells, macrophages, and cytologically benign small lymphocytes. Intermediate and large sized transformed lymphocytes are not seen. PTCLs, in contrast, contain cytologically atypical small and intermediate sized lymphocytes in addition to the atypical large forms.
Reed Sternberg cells typically express CD15, CD30, and nuclear Pax 5, and are CD45 negative. The neoplastic T cells of PTCL typically express CD45 and pan T cell antigens, often with aberrant loss of one of more. They are Pax5 negative. However, Reed–Sternberg cells may not express CD15 or nuclear Pax5 , and assessment of CD45 expression is often difficult because of its encirclement of R–S cells by CD45 positive T cells. Similarly, the loss of T cell antigens by PTCL cells can be extensive, obscuring lineage. Underappreciated in this setting is the value of CD43. Although CD43 is expressed by a wide range of hematopoietic cells in addition to T cells, it is not expressed on the membrane of R–S cells , but is expressed by the great majority of PTCLs.