Pathology of indolent B-cell neoplasms other than follicular lymphoma

An Unusual Case of Prolymphocytic Leukemia Transformation in a Patient With Chronic Lymphocytic Leukemia

B-cell prolymphocytic leukemia (B-PLL) is a rare leukemia characterized by rapidly increasing leukocytosis with splenomegaly and lymphadenopathy. Treatment strategies are largely based on studies of chronic lymphocytic leukemia (CLL). Antibodies against the cell surface protein CD20 are considered to be first-line therapy. A 76-year-old male with known CLL presented 2 weeks after starting chemoimmunotherapy for newly refractory CLL after failing ibrutinib therapy. White blood cell count was elevated at 226.7 × 10³/µL. Fluorescent in situ hybridization analysis of a bone marrow specimen showed new development of complex cytogenetics. Flow cytometry revealed B cells appearing slightly dimmer on CD45 and brighter on CD20 compared with typical B-CLL suggestive of less mature lymphocyte forms. The patient was diagnosed with B-PLL and started on obinutuzumab and venetoclax with rapid normalization of white blood cells. This case recapitulates the challenges in diagnosing and treating B-PLL. Ibrutinib resistance is a growing area of study with several proposed mechanisms of acquired resistance. The pathogenesis of B-PLL is not completely understood, although mutations in MYC are presumed to play a role.

B cell lymphoma with IRF4 rearrangement: A clinicopathological study of 13 cases

Interferon regulatory factor 4 (IRF4) rearrangement is commonly detected in patients with a range of lymphoproliferative malignancies, including myelomas, large B cell lymphomas and low-grade B cell neoplasms. However, IRF4 rearrangement is generally a relatively rare finding in these latter two cancer types. In the present article, we describe and summarize the clinicopathological and genetic features of 13 cases of B cell lymphoma with IRF4 rearrangement, including 12 cases of large B cell lymphoma and one case of low-grade lymphoma exhibiting such rearrangement. These cases were detected in six females and seven males between 14 and 71 years of age. From a morphological perspective, large B cell lymphoma tumors included in this analysis exhibited large neoplastic cells in diffuse or follicular patterns, while the case of low-grade lymphoma mainly composed of small lymphocytes. All analyzed cases exhibited a split in the IRF4 gene consistent with IRF4 translocation. Three of six analyzed large B cell lymphoma cases harbored IGLL5 mutations. Mutations in SAMHD1 were detected in the low-grade lymphoma with IRF4 rearrangement case. In summary, our results offer further insight into the morphological and molecular heterogeneity of cases of B cell lymphoma exhibiting IRF4 rearrangements.

Primary Low-Grade B-Cell Lymphoma of Skull With Translocation Between Immunoglobulin and Interferon Regulatory Factor 4 Genes

Low-grade B-cell lymphoma with immunoglobulin ( IG) and interferon regulatory factor 4 ( IRF4) gene rearrangement is extremely rare, with only 4 cases being previously reported. In this article, we report one additional case that arises from the skull and review the literature. The patient was a 69-year-old man who presented with recurrent and disabling vertigo and was found to have a 5.0 × 1.7 cm lesion within the left posterior parietal bone. Histological examination revealed a bone lesion with diffuse lymphoid infiltrate comprising of mostly small lymphocytes with scant cytoplasm, slightly irregular nuclei and inconspicuous nucleoli, and scattered larger cells resembling prolymphocytes and paraimmunoblasts. Immunohistochemical studies showed that the neoplastic cells were positive for CD20, CD79a, PAX5, CD23, CD43, BCL-2, BCL-6, MUM-1, LEF-1, and IgM and negative for CD5, CD10, cyclinD1, SOX11, and IgD. Flow cytometric analysis identified CD5 negative and CD10 negative monoclonal B cells with lambda light chain restriction. Fluorescence in situ hybridization analysis revealed del(13q) abnormality, but was negative for IGH/BCL2, IGH/CCND1, and BIRC3/MALT1 translocations. Next-generation sequencing identified IGK-IRF4 rearrangement and BRD4 E1113 del abnormalities. Given a low clinical stage (IE) of the disease, the patient did not receive additional treatments and was free of disease at 1 year after the diagnosis.

Richter Syndrome Presenting With Colon Localization

A 75-year-old man, who had been diagnosed with small lymphocytic lymphoma with cervical localization, underwent F-FDG PET/CT with iodinated contrast medium due to the appearance of cervical swelling suspected of illness relapse. PET/CT revealed intense F-FDG uptake in multiple cervical and subdiaphragmatic lymph nodes and in the left parotid. Moreover, diffuse uptake and wall thickening of the colon were evident; endoscopy with biopsy revealed a diffuse large B-cell lymphoma. Transformation into a more aggressive lymphoma occurs in 2% to 8% of small lymphocytic lymphoma, the so-called Richter syndrome. Extranodal localization in the sigmoid colon is an extremely rare site for transformed lymphoma.

Composite Nasopharyngeal plasmacytoma with nodal paraimmunoblastic variant of small lymphocytic lymphoma: A case report

A 78-year-old male who presented with severe shortness of breath and bilateral nasal congestion was shown to exhibit ta mass localized in the nasopharynx. The tumor was diagnosed as an extramedullary plasmacytoma. Peripheral blood eosinophilia had been persistently noted in the preceding 12 years. The plasmacytoma exhibited a predominance of κ-light chain monotypic Mott cells and was admixed with numerous eosinophils. No history of allergic rhinitis, asthma or aspirin sensitivity was elicited. An axillary lymph node was excised two weeks after the nasopharyngeal biopsy, and it exhibited a paraimmunoblastic transformation of small lymphocytic lymphoma. A review of the literature identified few occurrences of such simultaneous tumors in individual patients.