Summary In cases with low tumor burden or atypical morphologies, detection of the MYD88 L265P mutation using allele‐specific polymerase chain reaction can support the conclusive diagnosis of lymphoplasmacytic lymphoma/Waldenström macroglobulinemia.
Introduction
Lymphoplasmacytic lymphoma/Waldenström macroglobulinemia (LPL/WM) is an indolent B‐cell lymphoma that primarily involves the bone marrow (BM). It is characterized by plasmacytoid lymphocytes and monoclonal IgM gammopathy [ 1 ]. Unlike other plasma cell neoplasms, clinical complications such as hyperviscosity syndrome and renal impairment typically occur only when the IgM level exceeds 6 g/dL [ 2 ]. In addition, constitutional symptoms are infrequent in LPL/WM relative to other types of lymphoma, and many patients remain asymptomatic for prolonged periods. This indolent clinical course contrasts with the more aggressive presentation of other B‐cell lymphomas and contributes to the delayed diagnosis in early‐stage disease [ 3 ].
A hallmark molecular feature of LPL/WM is the MYD88 L265P mutation, which is present in approximately 93%–97% of cases [ 4 ]. However, diagnosis may be challenging when morphological features are atypical and molecular clonality is not initially evident. Furthermore, false‐negative results can occur with next‐generation sequencing (NGS), particularly when the tumor burden in the BM is low. In such cases, allele‐specific polymerase chain reaction (AS‐PCR) targeting the MYD88 L265P mutation may enhance diagnostic sensitivity [ 5 ].
Here, we describe a diagnostically challenging case of LPL/WM with atypical features, where the MYD88 L265P mutation was not detected by NGS but was revealed by AS‐PCR. This underscores the importance of sensitive molecular methods in atypical disease presentations.
Case History/Examination
A 74‐year‐old woman with a medical history of hypertension and atrial fibrillation, both managed with medication, presented to the emergency department with dyspnea. Her vital signs upon admission were: heart rate, 96 beats per minute; blood pressure, 96/54 mmHg; temperature, 36.8°C; oxygen saturation was 96% on room air; respiratory rate, 28 breaths per minute. She was alert but appeared visibly ill during the physical examination. Laboratory tests revealed leukocytopenia (leukocyte count, 1.91 × 10 9 /L), thrombocytopenia (platelet count, 39 × 10 9 /L), elevated C‐reactive protein level (7.48 mg/dL), and signs of acute renal injury (blood urea nitrogen, 97 mg/dL; creatinine, 2.67 mg/dL). A complete metabolic panel revealed: sodium, 140 mmol/L; potassium, 4.4 mmol/L; calcium, 10.5 mg/dL; total protein, 5.2 g/dL; albumin, 2.7 g/dL; aspartate aminotransferase, 176 IU/L; alanine aminotransferase, 50 IU/L; total bilirubin, 1.0 mg/dL. Serum protein electrophoresis identified a small monoclonal IgM kappa spike (190 mg/dL). BM aspiration showed 12.4% large monocytoid cells with cytoplasmic vacuolations (Figure 1 ). However, flow cytometry was inconclusive due to an insufficient number of gated cells.
Differential Diagnosis, Investigations and Treatment
IGH gene rearrangement testing, performed on DNA extracted from the BM cell pellet, confirmed B‐cell clonality (Figure 2 ). A BM biopsy revealed interstitial infiltration of CD20‐positive large cells (Figure 3A,B ). Computed tomography (CT) scans of the patient's abdomen upon admission showed hepatosplenomegaly and paraaortic lymphadenopathy. Chromosomal analysis demonstrated a complex karyotype indicative of malignant clones. Sanger sequencing and a targeted NGS panel for multiple myeloma using the Miseq Dx platform (Illumina, San Diego, CA, USA), including the MYD88 gene, revealed no pathogenic variants. However, AS‐PCR detected a faint but definitive band at the expected size (223 bp) for the MYD88 L265P mutation (Figure 4 ), confirming a diagnosis of LPL/WM. Primers used were as follows: wild‐type forward 5′‐GTGCCCATCAGAAGCGcCT‐3′; mutant‐specific forward 5′‐GTGCCCATCAGAAGCGcCC‐3′; common reverse 5′‐AGGAGGCAGGGCAGAAGTA‐3′ [ 5 ]. Both reactions generate a 223‐bp amplicon. Despite intensive supportive care, the patient developed progressive lactic acidosis and electrolyte imbalance.
Conclusion and Results
The diagnosis of LPL/WM with atypical morphology was confirmed only through AS‐PCR detection of MYD88 L265P. Despite diagnostic clarification, the patient's condition rapidly deteriorated, and she died on the hospital day 10. This case illustrates the critical importance of sensitive molecular testing for timely and accurate diagnosis in atypical presentations.
Discussion
We encountered a diagnostically complex case involving a patient with presumed LPL/WM who exhibited non‐classical features, including atypical BM morphology, low serum IgM concentration, and an unexpectedly rapid clinical progression. Despite clinical suspicion, initial molecular analyses using both Sanger sequencing and NGS failed to identify the MYD88 L265P mutation. Definitive confirmation was achieved only through AS‐PCR, emphasizing the critical role of high‐sensitivity assays in such diagnostically ambiguous presentations.
While NGS is a standard tool for detecting somatic mutations in hematologic malignancies, its performance may be suboptimal in specimens with low neoplastic content or compromised quality, such as hemodiluted BM aspirates [ 6 , 7 ]. Factors such as insufficient sequencing depth and the use of hybrid‐capture library preparation further diminish detection capability [ 8 ]. Amplicon‐based libraries have been shown to yield significantly higher coverage at target loci compared to hybrid‐capture methods, thereby enhancing analytical sensitivity [ 9 ]. Moreover, targeted approaches like AS‐PCR can detect MYD88 L265P at allele frequencies below 1%, rendering them particularly useful in low‐burden disease states [ 8 , 10 ]. In our case, reliance on a hybrid‐capture NGS panel likely contributed to the initial false‐negative result. Although AS‐PCR is highly sensitive, false‐negative results can still occur when the variant allele frequency is extremely low, the primer‐binding site is altered, or DNA quality is suboptimal. Under such conditions, orthogonal highly sensitive approaches should be pursued—digital droplet PCR (ddPCR), repeat AS‐PCR after enrichment of CD19‐positive B cells to increase the neoplastic DNA fraction, or high‐depth amplicon‐based NGS—to minimize the risk of false‐negative results and corroborate the molecular finding [ 11 , 12 , 13 , 14 ].
Morphologically, the BM was infiltrated by large atypical cells with monocytoid appearance and cytoplasmic vacuolations, mimicking features more typical of aggressive lymphomas. Immunophenotyping was limited due to low cellularity, further impeding initial diagnostic efforts. Nevertheless, the demonstration of B‐cell clonality via IGH gene rearrangement, together with AS‐PCR detection of the MYD88 L265P mutation, enables a confident diagnosis of LPL/WM. Previous reports have described similar diagnostic dilemmas, where AS‐PCR or ddPCR was instrumental in detecting the MYD88 L265P mutation from paucicellular or extramedullary specimens, such as pleural effusions or cerebrospinal fluid [ 15 ]. Although MYD88 L265P has been reported in splenic marginal zone lymphoma (SMZL) and activated B‐cell‐type diffuse large B‐cell lymphoma [ 16 , 17 , 18 ], the lack of dominant splenic involvement typical of SMZL and the absence of a discrete mass‐forming nodal lesion amenable to diagnostic biopsy argued against these entities in our patient, particularly when considering IGH clonality and the AS‐PCR finding favoring LPL/WM.
The aggressive clinical course in our case stands in contrast to the typically indolent behavior of LPL/WM. The patient experienced rapid deterioration and succumbed within 10 days of presentation, underscoring the potential for biological variability within this entity. Although uncommon, such fulminant cases highlight the urgency of prompt and accurate diagnosis to facilitate appropriate therapy.
Several limitations were evident in this case. Delayed molecular confirmation postponed the initiation of disease‐specific management, possibly contributing to the unfavorable outcome. The lack of immediate access to high‐sensitivity assays such as AS‐PCR at the time of initial testing hindered early diagnostic resolution. Additionally, limited BM cellularity restricted the utility of flow cytometry. Incorporating sensitive molecular platforms earlier in the diagnostic algorithm could improve recognition of atypical cases and guide timely therapeutic decisions. Moreover, expanding access to rapid and precise diagnostic tools may offer opportunities to better characterize and manage aggressive variants of LPL/WM.
In summary, this case reinforces the diagnostic utility of MYD88 L265P mutation testing through AS‐PCR in cases of LPL/WM, particularly those with atypical morphologies, low tumor burdens, and inconclusive results via standard testing. Incorporating sensitive molecular evaluation early during the diagnostic workup may prevent diagnostic delays and improve patient outcomes in diagnostically challenging LPL/WM cases.
Author Contributions
Ja Young Lee: conceptualization, funding acquisition, writing – original draft, writing – review and editing. Ha Young Park: data curation, visualization.
Ethics Statement
Ethical approval was waived by the local Ethics Committee of Inje University Busan Paik Hospital in view of the retrospective nature of the study and the fact that all the procedures being performed were part of routine care (No. BPIRB 2025‐04‐046).
Consent
This case report was conducted by institutional guidelines and was approved by the Institutional Review Board (IRB). As the patient had decreased, written informed consent for publication of this case report and accompanying images was obtained from the patient's son, who is the next of kin.
Conflicts of Interest
The authors declare no conflicts of interest.
Acknowledgments
We would like to thank Editage ( www.editage.co.kr ) for English language editing.
Data Availability Statement
No datasets were generated or analyzed during the current study.
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