Abstract and Introduction
Objectives: Epstein-Barr virus (EBV)–associated lymphoproliferative disorders (LPDs) encompass a group of well-defined entities of B-, T-, and natural killer (NK)–cell derivation. The diagnosis of these disorders is challenging because of clinical and morphologic features that may overlap with other benign and malignant EBV+ lymphoproliferations. This review describes our approach to the diagnosis of EBV-associated LPDs.
Methods: Two cases are presented that illustrate how we diagnose EBV-associated LPDs. The first case represents a systemic EBV+ T-cell lymphoma of childhood and the second case an EBV+ mucocutaneous ulcer. The clinicopathologic features that help distinguish these entities from biological and morphologic mimickers are emphasized.
Results: The accurate diagnosis of EBV-associated LPDs requires the incorporation of histologic and immunophenotypic features, the assessment of the EBV latency program, and, most important, complete clinical findings. Clonality analysis is not helpful in distinguishing benign from malignant EBV+ LPDs.
Conclusions: The better understanding of EBV-associated LPDs has resulted in the recognition of well-defined entities of B-, T-, and NK-cell derivation and consequently improvement of their treatment with curative intent. It is critical to distinguish benign from malignant EBV+ LPDs to avoid overtreatment.
Epstein-Barr virus (EBV)–associated B-, T-, and natural killer (NK)–cell lymphoproliferations have a broad clinical spectrum ranging from reactive self-limited disorders to malignant proliferations with a fulminant clinical course.[1–3] EBV is the most common viral infection in humans, with 95% of the population worldwide showing an asymptomatic lifelong carrier stage state.[4,5] Most EBV infections occur asymptomatically in children; however, a small subset of patients develops infectious mononucleosis (IM), a self-limited disease usually occurring in the second decade of life.[6,7] During EBV primary infection, the virus undergoes lytic replication in the epithelial cells of the oropharynx subsequently infecting circulating naive B cells. The latently EBV-infected B cells trigger a strong, specific primary cytotoxic response that controls the EBV infection. The quantity and the quality of the CD8+ T-cell response to EBV are critical to control the infection.[9,10] Patients with low numbers of EBV-specific CD8+ cells are prone to develop chronic active EBV infection (CAEBV). Furthermore, it has been shown that patients with CAEBV have a decrease in the T-cell receptor (TCR)–β repertoire and expanded T-cell clones in the peripheral blood. To escape immunosurveillance, EBV downregulates antigen expression, establishing a stable reservoir of memory B cells that carry the viral genome, but viral antigen expression is maximally suppressed, so-called latency 0.[13,14] There are three EBV latency patterns recognized.[4,5] Latency III involves the unrestricted expression of all nine latent genes (six EBV-encoded nuclear antigens [EBNAs] and three latent membrane proteins [LMPs]) observed during acute EBV infection or in severely immunodeficient individuals. Latency II is an intermediate pattern with expression of many latent proteins except for EBNA2. This pattern is demonstrated in most T-cell LPDs. Latency I is restricted to the expression of EBNA1, characteristic of Burkitt lymphoma. The transcription of nonpolyadenylated RNAs EBER1 and EBER2 is a constant feature of all latent EBV infection patterns and, therefore, is the best marker to demonstrate EBV infection in routine diagnosis.[1,2,15,16]
The exact mechanisms by which EBV promotes lymphomagenesis remain elusive; however, they involve impaired immune surveillance. The disruption of the finely regulated balance between virus and host immune system can result in EBV-associated lymphoproliferations of B-, T-, and NK-cell derivation, with disease manifestations generally depending on the type of EBV-infected cell and the state of host immunity Table 1 and Figure 1. The diagnosis of EBV-associated lymphoproliferative disorders (LPDs) may be challenging because it requires detailed clinical information and correlation of morphologic findings. In general, clonality analysis is not helpful in distinguishing benign from malignant EBV+ lymphoproliferations. In the assessment of EBV-associated LPDs, the investigation of EBV latency in tissue biopsy specimens (LMP1 and EBNA2) and peripheral blood (PB) EBV DNA copy numbers provides valuable information regarding the extent of host immunosuppression. In this review, we discuss the clinicopathologic features of EBV-associated LPDs and emphasize the differential diagnosis by describing two cases: (1) systemic EBV+ T-cell lymphoma of childhood and (2) EBV+ mucocutaneous ulcer (EBV+ MCU).
Differential diagnosis of EBER+ cells in lymph nodes and other tissues. The initial approach to the diagnosis of EBV+ lymphoproliferations is the identification of the cell type infected by EBV. The major criteria to identify the different disorders are depicted. EBV in T and NK cells is per default latency II. BCR, B-cell receptor; DLBCL, diffuse large B-cell lymphoma; EBV, Epstein-Barr virus; HLH, hemophagocytic lymphohistiocytosis; IM, infectious mononucleosis; LPD, lymphoproliferative disorder; LyG, lymphomatoid granulomatosis; NK, natural killer; NOS, not otherwise specified; RS-like, Reed-Sternberg–like cells; TCR, T-cell receptor.
Am J Clin Pathol. 2023;159(1):14-33. © 2023 American Society for Clinical Pathology