Acquired aberrant partial CD3 expression in recurrent Epstein-Barr virus-negative solitary plasmacytoma of tonsil

Abstract

The aberrant expression of specific T-cell maker CD3 in B-cell neoplasms can be a potential diagnostic pitfall leading to a misclassification of cell lineage. Here, we report a case of recurrent solitary plasmacytoma with new aberrant expression of CD3. The neoplastic plasma cells of the recurrent tumor were kappa restricted, positive for CD138, MUM1, negative for CD20, cyclin D1, and Epstein-Barr virus. CD79a was positive in majority of the tumor cells, except for a small focus which was strongly positive for CD3, but negative for other T-cell markers (CD2, CD5, CD7, CD4, and CD8) and CD56. The neoplastic plasma cells of the original tumor were negative for CD3. To the best of our knowledge, only one case of recurrent plasmacytoma with aberrant expression of CD3 has been published, which revealed disease progression in the recurrence. However, we did not observe morphologic evidence of disease progression in our case.

Keywords: CD3; Neoplasm, plasma cell; Plasmacytoma; T-cell antigen.

Fig. 1.

(A-C) Hematoxylin and eosin–stained slides from the recurrent plasmacytoma show well to moderately differentiated plasma cells. The neoplastic plasma cells are positive for MUM1 (D, E) and CD138 (F), negative for CD20 (G) and cyclin D1 (H). Proliferative index is about 5% by Ki-67 (I). The immunohistochemical staining is diffusely positive for kappa (J) while negative for lambda (K) which indicates the neoplastic plasma cells are kappa restrictive, and negative for Epstein-Barr encoding region in situ hybridization (L).

Fig. 2.

One focus of the neoplastic plasma cells in the recurrent plasmacytoma is with markedly reduced expression of CD79a (A, B), strongly positive for CD3 (D, E). CD79a is strongly positive in the CD3 negative plasma cells (C). CD3-positive plasma cells are positive for epithelial membrane antigen (G) with weak expression of IgG (H) and are the immunohistochemical staining is diffusely positive for kappa (I) while negative for lambda (J) which indicates the neoplastic plasma cells are kappa restrictive. Dominant cytoplasmic staining intensity of CD3 is in the neoplastic plasma cells (E) and dominant membranous staining intensity of CD3 is in the scattered normal T cells (F). There are no expressions of CD2 (K), CD4 (L), CD5 (M), CD7 (N), CD8 (O), and CD56 (P) in the neoplastic plasma cells of the recurrent plasmacytoma.

Fig. 3.

(A-C) Hematoxylin and eosin–stained slides from the original plasmacytoma show well to moderately differentiated plasma cells. The neoplastic plasma cells are positive for CD138 (D) and the immunohistochemical staining is diffusely positive for kappa (E) while negative for lambda (F) which indicates that the neoplastic plasma cells are kappa restrictive. The tumor cells are positive for CD79a (G), negative for CD2 (H), CD3 (I), CD20 (J), with weak expression of epithelial membrane antigen (K). Proliferative index is about 5% by Ki-67 (L).