Low-Grade Follicular Lymphoma with Highly Unusual Flow Cytometric, FISH, Molecular, and Classical Cytogenetic Results: A Case Report

Abstract

We present a low-grade follicular lymphoma case with highly unusual ancillary study results. The patient is a 50-year-old female with a 4.3 x 3.8 x 2.2 cm left inguinal mass, from which fine needle aspiration and excisional biopsy specimens were obtained. H&E sections showed effacement of the lymph node architecture by closely packed follicles comprised of mainly centrocytes and without tingible body macrophages. Immunohistochemical stains revealed the follicle cells positive for CD20, PAX5, BCL6, CD10 (weak), and BCL2 (weak), while CD3 highlighted small T lymphocytes mainly in the interfollicular areas. CD23 highlighted the follicular dendritic meshwork throughout. Flow cytometry study revealed an abnormal surface and cytoplasmic light chain negative B-cell population comprising approximately 60% of all events that expressed CD19, CD20, CD10, CD23 (partial), FMC-7, and CD38, while CD34, TdT, and CD5 were negative. The FISH panel revealed no IgH/BCL2, IgH/MYC, IgH/BCL6, IgH/MALT1 (18q21), or IgH/BCL1 translocations. No clonal IGH gene rearrangement was identified by Polymerase Chain Reaction (PCR). However, classical cytogenetic study found an abnormal karyotype: 46, XX, -12, +mar[6]. After literature review, this is the first known reported case of a low-grade follicular lymphoma with this constellation of findings.