Splenic B-cell leukemia/lymphoma with prominent nucleoli.

Abstract

Introduction
Splenic B-cell leukemia/lymphoma with prominent nucleoli is a recently defined mature B-cell neoplasm in the 2022 WHO classification (WHO-HAEM5), within the group of splenic B-cell lymphomas/leukemias. This entity arises in response to the limitations of the previous classification, in which diagnoses such as B-prolymphocytic leukemia (B-PLL) and the variant of hairy cell leukemia (HCL-v) showed significant clinical, morphological, and immunophenotypic overlap.¹

Clinical case
A 57-year-old patient with a history of smoking presented with a three-month history characterized by asthenia, adynamia, and diffuse abdominal pain. Evaluation revealed leukocytosis and marked splenomegaly. Laboratory results: Hct 20.5%; Hb 4.5 g/dL; leukocytes 496,000/mm³; platelets 52,000/mm³. LDH 595 IU/L.

Peripheral blood smear showed leukocytosis predominantly composed of medium-to-large cells, with a high nucleus-to-cytoplasm ratio due to nuclear predominance, loose chromatin, and a central nucleolus. Cytoplasm was scant to moderate, weakly basophilic, without evident granules. Cellular shadows (Gumprecht type) were present but not predominant. Mild to moderate anisocytosis. Thrombocytopenia. (Figure 1).

A whole-body CT scan (PanCT) demonstrated hepatomegaly and splenomegaly measuring 245 × 122 mm, with adenomegalies (8 mm) at the left axillary and inguinal levels.

Peripheral blood flow cytometry: 85.7% clonal B lymphocytes. Medium-sized cells: CD45++, CD19++, CD34(-), CD20++, CD38(-), CD5(-), CD10(-), CD23(-), CD79b+, CD200(-), CD43(-), CD31+, CD305++, CD11c(-), IgM(-), CD81++, CD62L+, CD95(-), with surface immunoglobulin light chain restriction (kappa).

Bone marrow biopsy: bone marrow infiltration (85%) by small B-cell lymphoma, CD20 positive. CD3: negative. CD10: negative. CD15: negative. CD30: negative. CD34: negative. CD45: positive. BCL6: negative. BCL2: positive. MUM1: negative. Ki67: 10% positive.

Molecular biology: TP53 mutated. CNS evaluation by flow cytometry showed involvement (53% clonal B lymphocytes with the same phenotype). Treatment with ibrutinib was initiated, and the patient is currently in complete remission.

Conclusion
Splenic B-cell neoplasms with prominent nucleoli represent a diagnostic challenge. In this case, diagnostic suspicion was supported by the concordance between clinical findings, cytomorphology, and flow cytometry (with absence of characteristic markers: CD5-, CD10-, CD23-), allowing the case to be oriented toward this entity despite the lack of a defining marker, highlighting the importance of an integrative approach for an accurate diagnosis.