It has been recognized that monoclonal gammopathy of undetermined significance (MGUS) precedes a diagnosis of plasma cell myeloma in most patients. Recent gene expression array analysis has revealed that an MYC activation signature is detected in plasma cell myeloma but not in MGUS. In this study, we performed immunohistochemical studies using membrane CD138 and nuclear MYC double staining on bone marrow biopsies from patients who met the diagnostic criteria of plasma cell myeloma or MGUS. Our study demonstrated nuclear MYC expression in CD138-positive plasma cells in 22 of 26 (84%) plasma cell myeloma samples and in none of the 29 bone marrow samples from patients with MGUS. In addition, our data on the follow-up biopsies from plasma cell myeloma patients with high MYC expression demonstrated that evaluation of MYC expression in plasma cells can be useful in detecting residual disease. We also demonstrated that plasma cells gained MYC expression in 5 of 8 patients (62.5%) when progressing from MGUS to plasma cell myeloma. Analysis of additional lymphomas with plasmacytic differentiation, including lymphoplasmacytic lymphoma, marginal zone lymphoma, and plasmablastic lymphoma, reveals that MYC detection can be a useful tool in the diagnosis of plasma cell myeloma.

Pancytopenia is regularly encountered in hematology practice, yet there exist few published assessments of the frequencies of various etiologies, and these frequencies exhibit substantial geographic variation. We reviewed bone marrow specimens from pancytopenic adults to determine the most common etiologies and to identify associations with clinical and laboratory findings. Of 132 patients with no history of hematolymphoid neoplasia, no prior bone marrow study for pancytopenia and no recent cytotoxic chemotherapy, 64% had clonal hematopoietic disorders. Most common were myeloid processes: 26% of patients had acute myeloid leukemia, and 17% had myelodysplasia. Less common were lymphoid neoplasms such as non-Hodgkin lymphoma (6%), hairy cell leukemia (5%) and precursor B acute lymphoblastic leukemia (4%). Among non-clonal cases, the most common specific diagnoses were aplastic anemia (5%), megaloblastic anemia (2%) and human immunodeficiency virus (HIV)-related changes (2%). Clonal diagnoses were associated with more severe cytopenias than non-clonal cases. Circulating nucleated erythroid precursors, immature granulocytes and blasts were seen more frequently in clonal cases. Nearly two-thirds of cases of new onset pancytopenia in adults in our North American practice setting have a clonal etiology, with myeloid neoplasms being most common. Blood counts and peripheral smear findings can provide insights into the likelihood of a clonal etiology.

Intravascular large B-cell lymphoma (IVLBCL) is a rare subtype of diffuse large B-cell lymphoma with an estimated incidence of less than one per million. Unlike other hematopoietic malignancies, lymphadenopathy and hepatosplenomegaly are uncommon, and patients typically present with nonspecific symptoms. IVLBCL presents a diagnostic challenge and patients are usually diagnosed late in the disease course, if at all, and the prognosis is poor. The differential diagnosis is broad, and physicians often pursue multiple diagnostic possibilities during patient workup. We present a case of IVLBCL discovered at autopsy in an 80-year-old male who presented with history and symptoms pointing to the tick-borne illness ehrlichiosis.