Plasmablastic Lymphoma, a Rare Entity in Bone Marrow with Unusual Immunophenotype and Challenging Differential Diagnosis

Abstract

Plasmablastic lymphoma (PBL) is an aggressive malignancy that usually occurs in the setting of immunosuppression. The immunohistochemical profile of PBL is that of terminally differentiated B lymphocytes. CD138, CD38, and MUM1 are usually immunopositive. However, pan B-cell markers such as CD20 and PAX-5 are usually negative.MYCrearrangement is the most commonly encountered genetic alteration, with immunoglobulin (IG), especially immunoglobulin heavy (IGH) chain, being the most frequent partner. We report a case of PBL in a 48-year-old human immunodeficiency virus- (HIV-) positive male who was admitted to the hospital with signs and symptoms suspicious for tumor lysis syndrome. Bone marrow examination revealed hypercellular marrow with trilineage hypoplasia and sheets of intermediate to large neoplastic cells with basophilic vacuolated cytoplasm comprising the majority of cellular elements of the bone marrow. The neoplastic cells were negative for conventional B-cell, T-cell, plasma cell, and myeloid markers, while flow cytometric analysis revealed an abnormal CD45-dim population that was partially weakly positive for CD71 and CD79b. The diagnosis was initially thought to be a high-grade primitive hematopoietic neoplasm, possibly an acute undifferentiated leukemia. BOB-1, however, was immunopositive in the neoplastic cells, confirming its B-cell origin. MYC was positive by immunohistochemistry and break-apart FISH, as were CD45, MUM-1, and EMA immunostains. There was immunoglobulin kappa (IGK) light chain gene rearrangement by polymerase chain reaction (PCR). Additionally, Epstein–Barr virus- (EBV–) encoded small RNAs (EBER) were positive by in situ hybridization (ISH). The tumor proliferation index by Ki-67 immunostaining approached 95%. Although the tumor cells were negative for CD38 and CD138, the diagnosis of PBL was still rendered. We recommend using a broad spectrum of B-cell markers, including BOB-1 and OCT-2, in such challenging cases of B-cell lymphomas with no expression of conventional B-cell markers. We also emphasize that the negative CD38 and CD138 should not exclude PBL from the differential diagnosis.

A 28-Year-Old Man With Mediastinal Seminoma Treated With BEP

“…CD45 (leukocyte common antigen) is a receptor-linked protein tyrosine phosphatase expressed in all leukocytes. Positive CD-45 examination is seen in 97% of B cells and in 90% of cell lymphomas (Alikhan et al 2016, Al Shaarani et al 2019, King & Lam. 2020).…”

Oral plasmablastic lymphoma in a HIV‐positive woman: Literature review and case report

“…Reports with insufficient clinical information of the patients were excluded. The literature review revealed 105 cases of HIV‐associated oral PBL in 46 published manuscripts 1,3,7–37 …”

Epstein-Barr virus-positive mucocutaneous ulcer, plasmablastic type, associated with nodal CD4+ angioimmunoblastic T-cell lymphoma and generalised pruritus: a self-limiting lymphoproliferative disorder resembling cutaneous plasmablastic lymphoma

“…The immunophenotype is similar to plasma cells: negative for CD45 with low/absent pan B-cell markers (CD20, CD79a and PAX5) and positive for plasma cell-associated markers (CD38, CD138 and MUM-1), with variable expression of immunoglobulins and negativity of bcl-6. Plasmablastic lymphoma showing aberrant expression of CD3 and CD411 or CD138 negativity12 has been described. C-myc rearrangements, particularly with translocation MYC-IGH (C-myc/immunoglobulin heavy chain), resembling Burkitt lymphoma, are cytogenetic abnormalities of note 7 9 10 13.…”

“…The most common location is the oral cavity1 3 4 7 9 10 and gastrointestinal tract,9 10 16 whereas the skin lesion has also been recorded 10 17. Bone marrow involvement is also encountered 12. It shows male predominance and the median age in the fourth and fifth decades of life.…”