In a patient with a normocellular bone marrow showing 8% lambda‑restricted plasma cells, low‑level IgH::CCND1 (t(11;14)) fusion, adequate iron stores, no ring sideroblasts, mild megakaryocytic atypia and thrombocytosis, and a negative JAK2, CALR, and MPL mutation panel, what is the appropriate diagnosis and management plan?

Diagnosis and Management of Plasma Cell Dyscrasia with t(11;14) and Concurrent Megakaryocytic Abnormalities

Primary Diagnosis

This patient has smoldering multiple myeloma (SMM) with t(11;14) translocation, and the thrombocytosis with megakaryocytic atypia represents a concurrent, likely reactive process that requires exclusion of an early myeloid neoplasm through next-generation sequencing. The 8% lambda-restricted plasma cells with IgH::CCND1 fusion meet criteria for a plasma cell dyscrasia, while the negative Congo red stain excludes AL amyloidosis and the megakaryocytic findings warrant separate investigation 1.

Plasma Cell Dyscrasia Classification

Diagnostic Criteria Met

• Lambda monoclonal plasma cells at 8% of nucleated cells confirmed by immunostains and flow cytometry establishes clonal plasma cell proliferation 1
• Low-level IgH::CCND1 fusion (t(11;14)) is the most common primary IGH translocation in multiple myeloma, present in 15-20% of cases, and represents a defining cytogenetic abnormality 1
• Negative Congo red stain definitively excludes AL amyloidosis, which would require immediate bortezomib-based therapy 1
• Normocellular marrow with trilineage hematopoiesis indicates preserved bone marrow function 1

Specific Classification: Smoldering Multiple Myeloma

The patient meets criteria for SMM rather than active myeloma because 1:

• Plasma cell percentage (8%) is below the 10% threshold typically required for symptomatic myeloma
• No mention of CRAB criteria (hypercalcemia, renal insufficiency, anemia, bone lesions)
• No evidence of end-organ damage attributable to the plasma cell disorder

Prognostic Implications of t(11;14)

The t(11;14) translocation carries intermediate to favorable prognosis in multiple myeloma 1:

• Results in CCND1 overexpression and is considered less aggressive than t(4;14), t(14;16), or t(14;20) 1
• Associated with increased sensitivity to BCL2 inhibition (venetoclax), which may inform future treatment decisions 1
• Patients with t(11;14) often exhibit lymphoplasmacytoid morphology 1

Evaluation of Thrombocytosis and Megakaryocytic Atypia

Differential Diagnosis

The mild thrombocytosis with megakaryocytic atypia requires systematic exclusion of a concurrent myeloid neoplasm, particularly given the negative JAK2, CALR, and MPL panel 1:

1. Myelodysplastic syndrome (MDS) with isolated megakaryocytic dysplasia:

   • Refractory thrombocytopenia (RT) subtype can present with thrombocytosis if treatment has normalized counts 1, 2
   • Requires ≥10% dysplastic megakaryocytes in a single lineage 1, 2
   • Micromegakaryocytes are highly specific for MDS 2, 3

2. Early/evolving myeloproliferative neoplasm (MPN):

   • Essential thrombocythemia remains possible despite negative driver mutations (10-15% are triple-negative) 1
   • Requires exclusion through bone marrow histology showing characteristic clustering and atypia 1

3. Reactive thrombocytosis:

   • Secondary to inflammation, infection, iron deficiency, or the plasma cell disorder itself 2
   • Should resolve with treatment of underlying cause 2

Critical Next Steps for Megakaryocytic Evaluation

Heme panel next-generation sequencing (NGS) is essential and correctly ordered 2, 3:

• Screen for MDS-associated mutations (SF3B1, ASXL1, TET2, SRSF2, U2AF1, RUNX1, TP53) 2, 3
• Detect MPN-associated mutations beyond the standard three (e.g., additional JAK2 exons, CSF3R) 1, 2
• Identify clonal hematopoiesis that may explain the megakaryocytic atypia 4

Peripheral blood smear review must specifically assess 2, 3:

• Presence of micromegakaryocytes (large monolobular or small binucleated forms) 2, 3
• Dysplastic neutrophils (pseudo-Pelger-Huët cells, hypogranulation) 2, 3
• Giant or hypogranular platelets 2, 3
• Any circulating blasts 2, 3

If NGS reveals clonal mutations or dysplasia persists, repeat bone marrow examination in 3-6 months to monitor for evolution of MDS or MPN 2, 3.

Management Algorithm

Immediate Actions (Within 2 Weeks)

1. Complete staging for smoldering myeloma 1:

   • Serum protein electrophoresis (SPEP) with immunofixation
   • 24-hour urine protein electrophoresis (UPEP) with immunofixation
   • Serum free light chain (FLC) assay with kappa/lambda ratio
   • Complete metabolic panel including calcium and creatinine
   • Complete blood count with differential
   • Beta-2 microglobulin and LDH
   • Serum albumin

2. Skeletal imaging 1:

   • Low-dose whole-body CT or whole-body MRI (preferred if available) to exclude lytic lesions
   • PET/CT if extramedullary disease is suspected

3. Await NGS results for megakaryocytic atypia evaluation 2, 3

Risk Stratification for Plasma Cell Dyscrasia

Assess high-risk features that would upgrade to active myeloma requiring treatment 1:

• Plasma cell percentage >10% (this patient has 8%)
• Serum M-protein >3 g/dL
• Involved/uninvolved FLC ratio >100
• Presence of additional high-risk cytogenetics (del(17p), t(4;14), t(14;16), gain/amp(1q), del(1p)) 1
• Focal lesions on MRI (≥1 lesion >5mm)

Surveillance Strategy for Smoldering Myeloma

If no high-risk features are present, observe with close monitoring 1:

• Repeat complete blood count, comprehensive metabolic panel, SPEP, and FLC every 3 months for first year
• Repeat skeletal imaging at 6 months, then annually
• Repeat bone marrow biopsy only if clinical progression suspected (rising M-protein, new cytopenias, symptoms)

If high-risk SMM criteria are met, consider clinical trial enrollment for early intervention with lenalidomide-based therapy 1.

Management of Thrombocytosis

If NGS is negative and reactive causes excluded 2, 3:

• Monitor CBC every 4-8 weeks for 6 months
• Repeat bone marrow in 3-6 months if thrombocytosis persists or worsens
• No specific therapy required if platelet count <600,000/μL and patient asymptomatic

If NGS reveals MDS-associated mutations 2, 3:

• Establish MDS diagnosis per WHO criteria (requires ≥10% dysplasia in one lineage or MDS-defining cytogenetics)
• Risk-stratify using IPSS-R score
• Refer to MDS specialist for consideration of hypomethylating agents or clinical trial

If NGS reveals MPN-associated mutations or triple-negative MPN confirmed by histology 1:

• Initiate aspirin 81 mg daily for cardiovascular risk reduction
• Consider cytoreduction (hydroxyurea) if platelet count >1,000/μL or thrombotic symptoms
• Refer to MPN specialist

Critical Pitfalls to Avoid

• Do not assume the thrombocytosis is reactive to the plasma cell disorder without excluding clonal myeloid disease through NGS and careful morphologic review 2, 3
• Do not initiate myeloma therapy for SMM outside of a clinical trial unless high-risk features or progression to active myeloma are documented 1
• Do not rely solely on JAK2 V617F, CALR, and MPL testing to exclude MPN; 10-15% of essential thrombocythemia cases are triple-negative 1
• Do not diagnose MDS based on single-lineage dysplasia alone; requires 6-month observation period if cytogenetics are normal 1, 2, 3
• Do not overlook the need for repeat bone marrow examination if the megakaryocytic atypia persists or NGS reveals clonal mutations 2, 3

Concurrent Dual Pathology Consideration

The coexistence of plasma cell dyscrasia and myeloid neoplasm is rare but well-documented 5, 4:

• Clonal hematopoietic mutations in lymphoid and myeloid lineages can occur concurrently 4
• Shared pathogenic mechanisms may link plasma cell disorders and MDS/MPN 4
• If both diagnoses are confirmed, manage each independently with appropriate specialists 1, 2