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Objectives: To evaluate clinicopathologic features, management, and behavior of colorectal extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT).Methods: Clinical data, laboratory studies, and radiographic records were reviewed (2005-2018), and fluorescence in situ hybridization studies were performed.Results: Eleven patients were identified, six of whom were discovered as an incidental finding on endoscopy. Morphologic and immunophenotypic features were similar to MALT lymphomas at other sites except that lymphoepithelial lesions were uncommon. Three of nine patients were positive for BIRC3/MALT1 fusions, two of whom had identical B-cell clones identified in subsequent gastric biopsy specimens. Eight of 10 patients had no clinically evaluable disease after observation (±antibiotics; n = 4) or radiation/chemotherapy (n = 4).Conclusions: Patients with incidental and localized colonic MALT lymphoma demonstrated an excellent prognosis with conservative management, although longer follow-up and data based on consistent staging and surveillance methods (including gastric evaluation) are necessary for informed management. [ABSTRACT FROM AUTHOR]

Objectives: Assessment for minimal/measurable residual disease (MRD) is a powerful prognostic factor in B lymphoblastic leukemia/lymphoma (B-LL/L) that is quickly becoming standard of care in assessing patients with B-LL/L posttherapy. MRD can be assessed using methodologies including flow cytometry and molecular genetics, with the former being rapid, relatively inexpensive, and widely applicable in many hematopathology/flow cytometry laboratories.Methods: This article presents an approach to MRD detection in B-LL/L by flow cytometry through case presentations with illustration of several potential pitfalls. We review normal maturation patterns, antigens used for assessment, flow panels that can be utilized, considerations to be made during therapy, and clinical impact. The benefits and drawbacks when using the "different from normal" and "leukemia associated phenotype" approaches are considered.Results: Evaluation for MRD in B-LL/L by flow cytometry relies on a knowledge of normal immunophenotypic patterns associated with B-cell maturation in states of rest and marrow regeneration so that one can identify patterns of antigen expression that differentiate abnormal, leukemic populations from regenerating hematogones or B-cell precursors. The nature of therapy can affect normal patterns, a phenomenon especially important to take into consideration given the increased use of targeted therapies in the treatment of B-LL/L.Conclusions: Flow cytometry is widely available in many laboratories and is a cost-effective way to evaluate for B-LL/L MRD. However, panel validation and interpreter education are crucial for accurate assessment. [ABSTRACT FROM AUTHOR]

Objectives: Given the increased complexity of molecular and cytogenetic testing (MOL-CG), the Society for Hematopathology Education Committee (SH-EC) was interested in determining what the current expectations are for MOL-CG education in hematopathology (HP) fellowship training.Methods: The SH-EC sent a questionnaire to HP fellowship program directors (HP-PDs) covering MOL-CG training curricula, test menus, faculty background, teaching, and sign-out roles. These findings were explored via a panel-based discussion at the 2018 SH-EC meeting for HP-PDs.Results: HP fellows are expected to understand basic principles, nomenclature, and indications for and limitations of testing. Interpretation of common assays is within that scope, but not necessarily proficiency in technical troubleshooting of testing or analysis of complex raw data.Conclusions: The consensus was that HP fellows should understand the components of MOL-CG testing necessary to incorporate those results into an accurate, clinically relevant, and integrated HP report. [ABSTRACT FROM AUTHOR]

Distinguishing neoplastic from reactive cutaneous lymphoid infiltrates remains a diagnostic challenge. While flow cytometry is broadly used in hematopathology, it is only now emerging as a method for determining the immunophenotype and clonality of cutaneous lymphocyte populations. Cutaneous marginal zone lymphomas are particularly challenging; these cases often have lymphoid follicles with reactive features, and the neoplastic cells can be greatly outnumbered by the associated reactive, polyclonal B- and T-lymphocyte populations. We present the case of a 53-year-old man who presented with a three-year history of a patch on the left cheek. Two biopsies, taken a year apart, showed a dense nodular superficial and deep perivascular, perifollicular, and peri-eccrine mixed lymphoid infiltrate (60% B-cells and 40% T-cells), composed mainly of small lymphocytes with focal reactive germinal centers. These findings were initially interpreted as being most consistent with a reactive process, or pseudolymphoma. Because the lesion failed to regress after multiple steroid injections, a third biopsy was taken. Although this specimen had similar morphologic features, flow cytometry was performed and revealed a small abnormal B-cell population comprising 1.14% of total white blood cells. These B-cells showed abnormal expression of CD11c and were lambda light chain restricted with normal expression of CD19, CD20, CD38, and CD45 without CD5, CD10, or CD43. In addition, a small lambda light chain restricted plasma cell population was identified (0.01% of total white blood cells). No abnormal T-cells were identified. Molecular studies confirmed the presence of a clonal immunoglobulin gene rearrangement. Taken together, these findings were interpreted as cutaneous marginal zone lymphoma; the patient was then referred to oncology for staging and further management. The case underscores the limitations of morphology and immunohistochemistry alone in the diagnosis of cutaneous lymphomas and demonstrates the sensitivity of flow cytometry in detecting small, abnormal lymphocyte populations that might otherwise be overlooked. [ABSTRACT FROM AUTHOR]