Blastoid Variant Mantle Cell Lymphoma Expressing Aberrant CD3 and CD10 with Concurrent Small Lymphocytic Lymphoma: Establishment of a Clonal Relationship by B- and T-Cell Receptor Gene Rearrangements.

Mantle cell lymphoma (MCL) is an aggressive non-Hodgkin B-cell lymphoma typically expressing CD19, CD20, CD5, FMC-7, CyclinD1, and SOX-11 and harboring the IgH/CCND1 translocation. We report a blastoid variant of mantle cell lymphoma (MCL) involving an inguinal lymph node that, in addition to classical phenotypic and genetic findings, also aberrantly coexpresses surface CD10 and cytoplasmic CD3. Small lymphocytic lymphoma (SLL) was also present in the same lymph node and in the bone marrow. B- and T-cell gene rearrangement studies by PCR show the MCL and SLL to be clonally related. Expression of multiple aberrant antigens and concurrent lymphomas of different classifications can cause a diagnostic challenge. Awareness of such a presentation and integration of the data from morphologic evaluation, flow cytometry, immunohistochemistry, and FISH studies is required for proper diagnosis, prognosis, and therapy.

The B-cell transcription factors BSAP, Oct-2, and BOB.1 and the pan-B-cell markers CD20, CD22, and CD79a are useful in the differential diagnosis of classic Hodgkin lymphoma.

Even with routine immunohistochemical evaluation, distinguishing classic Hodgkin lymphoma (CHL) from diffuse large B-cell lymphoma (DLBCL) or anaplastic large cell lymphoma (ALCL) can be difficult. In these cases, the transcription factors (B cell-specific activator protein [BSAP], octamer-binding transcription factor 2 [Oct-2], and B-cell Oct-binding protein 1 [BOB.1]) and the pan-B-cell markers (CD20, CD22, and CD79a) may aid in clarifying the diagnosis. In 57 cases of CHL, 5 cases of nodular lymphocyte predominant Hodgkin lymphoma (NLPHL), and 33 cases of non-Hodgkin lymphoma (25 DLBCL and 8 ALCL) we found the transcription factor phenotype BSAP+ and either Oct-2- or BOB.1- to be predictive of CHL; BSAP+/Oct-2+/BOB.1+ was predictive of NLPHL or DLBCL, while BSAP- was predictive of ALCL. Expression of all 3 pan-B-cell markers was seen only in NLPHL and DLBCL; positivity for a single B-cell marker was present only in CHL. Thus, together, the transcription factors and pan-B-cell markers might be useful in the differential diagnosis of CHL.

Immunohistochemical expression of the transcription factor DP-1 and its heterodimeric partner E2F-1 in non-Hodgkin lymphoma.

DP-1 is a G1 cell cycle-related protein that forms heterodimers with E2F, a family of transcriptional factors regulating the expression of genes important for G1 to S progression. Although the exact role of DP-1 is not well understood, it has been shown to stabilize DNA binding of E2F proteins. By immunohistochemistry, the authors examined the expression of DP-1 in lymphoid tissues, including 8 cases of reactive follicular hyperplasia and 69 cases of B-cell non-Hodgkin lymphoma. The expression of the cell cycle-related proteins E2F-1 and Ki-67 was also assessed. Scoring was based on the proportion of labeled nuclei (1-10%, 11-25%, 26-50%, and > 50%). In reactive follicular hyperplasia, staining for DP-1, E2F-1, and Ki-67 was largely confined to the germinal centers. All 25 cases of follicular lymphoma, regardless of grade, had a high proportion (> 50%) of DP-1-positive cells but a lower proportion of cells marking for E2F-1 and Ki-67 (P < 0.001). The diffuse large B-cell lymphomas (n = 24) had high DP-1 and Ki-67 scores but low E2F-1 scores (P < 0.001). Small lymphocytic (n = 10), marginal zone (n = 3), and mantle cell lymphomas (n = 5) contained relatively low proportions of cells labeled for all three markers. Precursor B-cell lymphoblastic lymphoma (n = 2) displayed high proportions of cells positive for DP-1, Ki-67, and E2F-1 (> 50% in both cases). Except in follicular center cell lesions, DP-1 expression generally correlated with that of Ki-67. However, the expression of DP-1 was discordant with that of E2F-1 in benign and malignant follicular center cells, suggesting that DP-1 may have functions other than facilitating E2F-1-dependent gene regulation and cell cycle progression in these neoplasms.