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Context.--Plasma cell myeloma and chronic lymphocytic leukemia are both common hematologic malignancies, sharing many epidemiologic features. Concomitant detection of the 2 conditions poses special diagnostic challenges for the pathologist. Objective.--To describe the pathologic findings in cases of concomitant bone marrow involvement by myeloma and [CD5.sup.+] monoclonal B cells and to outline the differential diagnostic possibilities, suggest a workup for correct diagnosis, and examine clinical outcome. Design.--Fifteen cases that met the diagnostic criteria were identified from pathology databases at 4 participating institutions. Morphologic findings were reviewed, additional immunohistochemical stains performed, and flow cytometric, cytogenetic, and relevant laboratory and clinical information was summarized. Previously published cases were searched from electronic databases and cross-references. Results.--Most patients (13 of 15) were older males. Often (11 of 15) they presented clinically with myeloma, yet had both monotypic plasma cells and B cells in the diagnostic marrow. In 4 patients, myeloma developed 24 months or later after chronic lymphocytic leukemia. In 7 patients, myeloma and [CD5.sup.+] B cells showed identical immunoglobulin light-chain restriction. Primary differential diagnoses include lymphoplasmacytic lymphoma, marginal zone lymphoma, and chronic lymphocytic leukemia with plasmacytoid differentiation. CD56 and/or cyclin D1 expression by plasma cells was helpful for correct diagnosis. Most patients in our cohort and published reports were treated for plasma cell myeloma. Conclusions.--Concomitant detection of myeloma and chronic lymphocytic leukemia in the bone marrow is a rare event, which must be carefully differentiated from lymphomas with lymphoplasmacytic differentiation for correct treatment. (Arch Pathol Lab Med. 2013;137:503-517; doi: 10.5858/arpa.2011-0696-OA), Plasma cell myeloma (PCM) (or multiple myeloma) and chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL) are both common hematologic neoplasms, each constituting about 10% to 11% of all hematologic malignancies. (1,2) [...]

* Context.--Marginal zone lymphomas (MZLs) are the most common lymphomas encountered in the orbit and ocular adnexa. The accurate categorization of these lymphomas is critical to avoid undertreatment or overtreatment. Objective.--To identify features of orbital MZLs that distinguish them from other lymphomas and reactive lymphoid infiltrates and support the categorization of orbital MZL as mucosa-associated lymphoid tissue (MALT)-type MZLs. Design.--Biopsies from 149 patients with lymphoid lesions of ocular adnexa were examined. Additional immunohistochemical stains and fluorescence in situ hybridization study for the MALT1 locus were performed in selected cases, and patient charts were reviewed. Results.--A total of 115 lymphomas and 34 reactive infiltrates were identified, of which B-cell lymphomas constituted 92% and MZLs constituted 54% of all lymphomas. Certain clinical features (young age, race, bilaterality) favored a reactive infiltrate, but none were diagnostic. Histologic features, such as infiltrative lesions, reactive B-cell follicles, and lymphoepithelial lesions, overlapped between reactive infiltrates and conjunctival MZL. In contrast to conjuctival MZL, orbital MZL infrequently showed reactive follicles, rarely showed epithelial tissue, and did not show lymphoepithelial lesions. Cytogenetic abnormality involving the MALT1 locus was demonstrated in only 15% of ocular adnexal MZLs. Conclusion.--Many MZLs of orbital soft tissue lack key features associated with MALT-type MZL, and the designation MALT lymphoma should be avoided in their diagnosis. (Arch Pathol Lab Med. 2008;132:1405-1416), Lymphoid infiltrates of the conjunctiva and orbit occur frequently, and it has long been recognized that the differentiation of benign infiltrates from malignant lymphomas can be challenging not only for [...]