Aberrant expression of napsin A in a subset of malignant lymphomas

Napsin A is commonly expressed in pulmonary adenocarcinomas and some renal cell carcinomas. However, napsin A expression in lymphoid neoplasms has never been reported.

Glycoproteomic analyses of lymphoma-derived cell lines revealed napsin A expression in anaplastic large cell lymphoma (ALCL) cells. We thus investigated napsin A expression in lymphoid neoplasms. A variety of lymphomas (n=672) and histiocytic tumors (n=55) was immunostained for napsin A using patient tissues.

In reactive lymphoid tissues, only a few histiocytes were positive for napsin A. ALK-positive ALCLs most frequently expressed napsin A (34.4%, 11/32 cases) at a rate that was significantly higher compared with ALK-negative ALCL (8.6%, 3/35; P=0.015). Napsin A expression was also observed in 13.4% (20/149) of diffuse large B-cell lymphomas (DLBCL), 11.1% (15/134) of Hodgkin lymphomas, 4.9% (2/41) of follicular lymphomas, 6% (4/67) of peripheral T-cell lymphomas, and 3.8% (1/26) of plasma cell neoplasms. Otherwise, napsin A was not detected in any other types of lymphomas or histiocytic neoplasms. Napsin A expression in systemic ALCL was associated with a higher international prognostic index. ALCL and DLBCL patients with napsin A expression tended to have poor prognosis.

These results demonstrated that napsin A is aberrantly expressed in a subset of lymphomas. The biological significance of napsin A in lymphomas warrants further study.