Mantle cell lymphoma. (A) Histologic section from a submandibular gland biopsy specimen demonstrating an abnormal diffuse infiltrate of small to intermediate-size lymphoid cells. Several mitotic figures are present. Hematoxylin & eosin stain, magnification ×40. (B) Representative flow cytometric dot plots with population of interest highlighted in green: CD19 versus CD5 demonstrates CD5⁺ B-cell population with weak intensity staining for CD19; FMC-7 versus CD5 demonstrates positivity for FMC-7; CD20 versus kappa and CD20 versus lambda demonstrate moderate intensity staining for CD20 and kappa immunoglobulin light chain restriction. In addition, B cells were CD10⁻ and CD23⁻ (data not shown). The flow cytometric data was acquired using a BD FACS Calibur flow cytometer (BD Biosciences, San Jose, CA) and the dot plots were created using BD FACSDiva software v5.0.2 (BD Biosciences). (C) Cyclin-D1 paraffin section immunohistochemical stain, demonstrating many positive cells with characteristic nuclear staining; magnification ×40. (D) FISH studies demonstrating the IGH/CCND1 [t(11,14)(q13;q32)] rearrangement. Hybridization with the LSI IGH/CCND1-XT dual color, dual fusion DNA probe demonstrates one green signal from the unrearranged chromosome 14q32, one red signal from the unrearranged 11q13, and 3 fusion signals: one from the derivative chromosome 11, one from the derivative chromosome 14, and an extra signal suggesting the presence of an additional copy of all or part of one of the derivative chromosomes involved in the IGH/CCND1rearrangement. Courtesy of the Pittsburgh Cytogenetics Laboratory, Magee-Womens Hospital, Pittsburgh, PA. The images were taken through an Olympus BX40 microscope (Olympus, Tokyo, Japan) and acquired with a SPOT Insight 2 megapixel 3-shot color camera and SPOT Advanced imaging software (Diagnostic Instruments, Sterling Heights, MI).