Plasmablastic Transformation of CLL/SLL: The Role of Early NGS Diagnosis and Targeted Multimodal Therapy

1. Introduction

Richter’s transformation (RT) is the progression of chronic lymphocytic leukaemia/small lymphocytic lymphoma (CLL/SLL) into a more aggressive lymphoma, most often diffuse large B-cell lymphoma (DLBCL) [1]. Plasmablastic lymphoma (PBL) is a rare and aggressive transformation, especially uncommon in immunocompetent individuals [2]. It is most often seen in the context of immunodeficiency, such as HIV infection or prior exposure to chemotherapy [3,4,5]. We report a rare synchronous SLL and PBL case in an immunocompetent patient, and we additionally analyzed published cases CLL/SLL-to-PBL transformations, focusing on their clinical presentation, diagnostic features, and therapeutic approaches, highlighting patterns relevant for early recognition and management.

2. Case Report

We report a rare case of synchronous SLL and PBL in a 46-year-old woman, who presented in December 2023 with lower back pain, highlighting both diagnostic challenges and histopathological features. PET imaging revealed hypermetabolic retroperitoneal masses compressing the right ureter without renal impairment, along with bilateral pelvic lymph node involvement. In January 2024, an axillary lymph node biopsy was performed due to accessibility and significant lymphadenopathy on imaging, concurrently with a biopsy of a retroperitoneal lymph node. Biopsy specimens were analyzed histologically and immunohistochemically. Axillary and retroperitoneal nodes were examined for morphology and immunophenotype using standard panels (CD20, CD5, CD23, CD10, BCL6, cyclin D1, CD138, CD38, MUM1, c-myc, Ki67, light chains). FISH analysis was performed to detect MYC, BCL2, and BCL6 rearrangements. Clonal relatedness between SLL and PBL components was assessed by PCR-based analysis of IGH, IGK, and IGL loci, complemented by next-generation sequencing (NGS) of IGHV. In situ hybridization for EBV (EBER) and HHV8 (LANA1) was also performed. The patient was treated with Dara-CHOP chemotherapy (daratumumab, cyclophosphamide, doxorubicin, vincristine, prednisone) followed by autologous hematopoietic stem cell transplantation (AHSCT). Maintenance therapy consisted of monthly daratumumab and ibrutinib.

Overview of clinical and pathological features of reported transformation cases from CLL/SLL to PBL were analyzed separately for synchronous and metachronous transformations. Synchronous cases were defined as those in which CLL/SLL and PBL were diagnosed simultaneously or within a 6-month interval, while metachronous cases were defined as those in which transformation occurred more than 6 months after the initial CLL/SLL diagnosis.This distinction was made because synchronous transformations, occurring within a short temporal window, are more likely to originate from the same precursor clone, whereas metachronous cases may develop through later genetic divergence or therapy-driven clonal evolution, making their clonal relationship less predictable unless formally confirmed by molecular testing. For both groups, we collected and compared available clinical characteristics, pathological findings, immunophenotypic profiles, molecular data, treatment approaches, and patient outcomes, as reported in the literature.

3. Results

3.1. Morphological and Immunohistochemical Evaluation

Axillary lymph node biopsy revealed diffuse infiltration by small neoplastic cells with round to slightly irregular nuclei, condensed chromatin, and scant cytoplasm (Figure 1A). Immunohistochemistry confirmed SLL/CLL phenotype: CD20+, CD5+, CD23+, CD10−, BCL6−, cyclin D1−. Ki67 proliferation index was low (20–30%), with focal enhancement in proliferative centers (Figure 1B–F). Retroperitoneal lymph node histology showed a compact lymphoid proliferation of medium to large plasmacytoid cells with rounded/angular nuclei, decondensed chromatin, and prominent nucleoli. Apoptotic debris and mitoses were observed. Tumor cells were CD138+, CD38+, MUM1+, c-myc+, CD5−, CD10−, CD19−, CD20−, CD23−, CD45−, BCL2−, BCL6−, EMA−, cyclin D1−, ALK1−, IgA−, OCT2−, LANA1−. Ki67 index was nearly 100%. Tumor cells expressed lambda light chains, negative for kappa (Figure 2A,B).

3.2. Mollecular Analysis

FISH analysis detected MYC rearrangement in PBL; BCL2 and BCL6 translocations were absent (Figure 3A–C). PCR and NGS demonstrated identical IGHV1-69/IGHD3/IGHJ6 rearrangement in both SLL and PBL, confirming clonal relatedness and Richter transformation (Figure 4). EBV and HHV8 were negative.

3.3. Therapy

After two cycles of Dara-CHOP, PET in March 2024 showed no progression but persistent hypermetabolic lesions, prompting four additional cycles. By May 2024, a complete metabolic response was observed in the abdominal mass, though pelvic lymphadenopathy remained metabolically active. In July 2024, the patient underwent AHSCT. Chemotherapy was well tolerated; aplasia occurred on day +2, G-CSF started on day +7, with uneventful recovery. Maintenance therapy was initiated for residual SLL/CLL with daratumumab and ibrutinib.

3.4. Brief review of Synchronous Versus Metachronous Transformations Reported in the Literature

The results of our literature review are presented in Table 1 and Table 2. In summary, we identified four simultaneously diagnosed transformation cases within less than six months and ten non-simultaneously diagnosed cases. In both groups, patients were predominantly elderly males, with heterogeneous clinical presentations, diagnostic approaches, and treatment modalities. CHOP-based regimens were the most frequently applied therapy. In the synchronous group, only our patient achieved clinical stability with a daratumumab-based regimen targeting CD38 in addition to prior CHOP therapy, whereas in the metachronous group, one patient responded to combined localized therapy and chemotherapy.

4. Discussion

PBL is a rare and aggressive B-cell neoplasm first described by Delecluse et al. in 1997, predominantly affecting older male patients and immunocompromised individuals such as those with HIV, EBV infection, or post-transplant immunosuppression [3,4,6,7]. Extranodal involvement is common, while purely nodal PBL in immunocompetent patients remains exceedingly rare [3,8,9]. Transformation of CLL/SLL into PBL is particularly uncommon. The first reported case was described by Robak et al. in 2001 in an HIV- and EBV-negative woman [10]. Early (≤6 months) versus late (>6 months) transformations may reflect distinct biological mechanisms: early transformation could result from a pre-existing aggressive sub-clone or a common progenitor at the time of CLL diagnosis, whereas late transformation may arise from clonal evolution under therapeutic or micro-environmental pressure, as we revised the cases [4,7] (Table 1 and Table 2). Precise diagnosis typically involves lymph node biopsy, supported by ancillary studies such as IHC, FISH, PCR, and NGS to confirm clonality [2,16,18,19,20]. We report a rare case of a middle-aged woman who presented with lumbar pain, bilateral renal obstruction, and generalized lymphadenopathy. SLL and PBL were diagnosed simultaneously from axillary and retroperitoneal lymph nodes. While most reported patients are older males, only a few female cases—including ours—have been described [11,12]. The clinical presentation in our patient, with generalized lymphadenopathy and lumbar pain, aligns with the most commonly reported manifestations in the literature, which often also include B symptoms and pain associated with retroperitoneal or skeletal involvement [13,14]. Unlike most reported cases, the transformation in our patient was confined to lymph nodes, with no bone marrow involvement. This localized presentation may indicate an early stage of transformation or a nodal form of PBL with distinct biological behavior, and it may also reflect the benefit of rapid and accurate diagnostic evaluation. The diagnosis was established using a complete diagnostic workup—including imaging, immunohistochemistry, and FISH—with clonal relatedness confirmed by PCR and next-generation sequencing, representing, to our knowledge, the first such comprehensive approach reported in the literature. Histologically, the axillary lymph node showed classic SLL features with CD20 and CD5 expression. In contrast, the retroperitoneal lymph node demonstrated a diffuse proliferation of large plasmablast- and immunoblast-like cells with high mitotic activity and necrosis. These cells expressed plasma cell markers CD38, CD138, and MUM1, had a high Ki-67 index, and lacked B-cell markers such as CD20 and PAX5, consistent with typical PBL [3,4,7]. Because PBL can overlap morphologically and immunophenotypically with other entities—including immunoblastic DLBCL, plasmablastic myeloma, ALK-positive large B-cell lymphoma, and HHV-8–associated DLBCL—these diagnoses were carefully excluded. In our case, ALK positivity and paraproteinemia were absent, and lack of BCL2 and BCL6 expression helped rule out DLBCL and Burkitt lymphoma, while positivity for MYC and plasma cell markers supported the diagnosis of PBL [3,15]. Consistent with other reports, our patient tested negative for HIV, EBV, and HHV-8. Although HIV status is often negative or unreported in the literature, EBV positivity has been described by Khanna et al. and Martinez et al. ([2,12]; Table 1 and Table 2). These observations suggest that some cases of PBL may arise independently of viral infection, potentially driven by somatic mutations, genomic instability, and MYC-mediated transformation. Using FISH, we confirmed a MYC rearrangement, in line with the majority of previously reported cases ([2,10,16,17]). In contrast, Gasljevic et al. described a case without MYC rearrangement, highlighting potential diagnostic challenges, particularly as the antecedent disease was classical Hodgkin lymphoma rather than CLL/SLL ([11]; Table 2).

Confirming clonal relatedness through PCR and NGS was essential to establish this case as a true Richter transformation rather than two unrelated neoplasms ([2,16,18]). While Ramsay et al. and Chan et al. previously applied NGS, their analyses were limited to metachronous cases ([17,18]; Table 2). NGS is particularly valuable in synchronous transformations, where histopathological and immunophenotypic overlap can obscure disease evolution and where molecular confirmation is necessary to distinguish true transformation from the coexistence of two independent lymphoid neoplasms. In these instances, high-resolution genomic analysis provides definitive evidence of clonal relatedness, improves understanding of pathogenesis, and informs more tailored therapeutic strategies ([19,20]). Although additional synchronous transformation cases have been reported ([8,21,22]), they were excluded from our review due to lack of clonality confirmation, limiting their interpretive value.

Therapeutic management of PBL remains challenging due to its intrinsic chemo-resistance, MYC rearrangements, plasmacytic phenotype, and often low CD20 expression, which reduces rituximab efficacy [10,18]. In most reported cases, patients received R-CHOP or CHOP-like regimens and succumbed within six months, with only two exceptions: one patient survived 24 months, and another remained stable at the time of publication ([12,9]; Table 2). A particularly unusual case, reported by Mazumder et al. but not included in our review due to unconfirmed clonality, involved spontaneous regression of a gingival mass following biopsy [21]. However, the diagnostic work-up was limited to histology and EBV positivity, without molecular or phenotypic profiling, leaving its classification uncertain. In contrast to most reviewed cases, particularly synchronous transformations, our patient was diagnosed approximately 24 months ago and remains clinically stable after completing eight cycles of chemotherapy. She was treated with a daratumumab-based regimen targeting CD38, a marker highly expressed in PBL, which led to rapid resolution of lymphadenopathy, hepatosplenomegaly, and systemic symptoms. The patient subsequently underwent ASCT and is maintained on daratumumab and ibrutinib. This multimodal approach appears effective in controlling both plasmablastic and residual B-cell components. These observations emphasize the importance of tailoring treatment to the plasmablastic phenotype, particularly through the use of CD38-targeted therapy, BTK inhibitors, and stem cell transplantation.

5. Conclusions

This report describes a rare synchronous transformation of CLL/SLL into PBL in an immunocompetent woman, with nodal disease and clonal relatedness confirmed by PCR and NGS. Early molecular confirmation allowed prompt initiation of targeted multimodal therapy, resulting in a favorable outcome. These findings underscore the value of precise molecular diagnostics in synchronous transformations and the potential efficacy of CD38- and BTK-directed treatments in plasmablastic disease.