CD30-positive DLBCL with microvillous features: So-called microvillous lymphoma

Aimin Liu ^1*, Yuichi Sugisaki ², Masaru Hosone ², Shigeki Namimatsu ², Shotaro Maeda ², Zenya Naito ² and Mohammad Ghazizadeh ¹

¹ Central Institute for Electron Microscopic Researches, Nippon Medical School, Tokyo, Japan
² Department of Pathology, Nippon Medical School, Tokyo, Japan

^* To whom correspondence should be addressed. E-mail: aimin{at}nms.ac.jp.

Accepted 12 August 2008

Abstract

Abstract Microvillous Lymphomas (MVLs) are a rare entity, and currently considered as an unusual morphologic variant of diffuse large B-cell lymphoma (DLBCL) characterized by a cohesive sinusoidal growth pattern and ultrastructural microvillous projections. Most MVLs are negative for CD30. Only a few cases of MVLs with CD30 positivity have been reported in the literature. We present one case of CD30-positive MVLs in an 87-year-old man who was encountered generalized lymphadenopathy. Histopathologically, the tumor showed a morphologic mimic of anaplastic large cell lymphoma (ALCL) with sinusoidal growth pattern. Immunohistochemically (IHC), the tumor cells were CD30+, CD20+, CD45+, BCL-2+, BCL-6+, MUM1+, Ki-67+, CD45RO-, CD3-, CD10-, CD15-, CD56-, EMA-, TIA-1- and ALK-. Flow cytometry analysis (FCM) result was confirmed the IHC. In situ hybridization for Epstein-Barr (EB) virus RNA was negative. Electron microscopically (EM), the tumor cells were similar to large transformed lymphocytes and had circumferentially profuse microvillous projections resembling those of epithelial mesothelioma cells. In conclusion, CD30-positive MVLs are indistinguishable from ALCLs that have ultrastructual microvillous projections by morphology alone. However, the lack of EMA, TIA-1 and ALK expression in our MVL case facilitated a definite distinction from ALCLs. The results of a panel of 3 markers (CD10-, Bcl-6+ and MUM1+) suggested that the present case of CD30-positive MVLs has an activated non-germinal center (GC) B-cell origin.