Sections of the endotracheal mass revealed the characteristic findings of hyaline-vascular CD, including reactive lymphoid follicles with small hyalinized germinal centers surrounded by small lymphocytes in a concentric fashion, prominent interfollicular vascularity, and hyalinized thick-walled blood vessels penetrating the mantle zones and germinal centers (“lollypop” appearance) [Fig 2
]. There were prominent pale cuffs of small to medium-sized lymphocytes without significant cytologic atypia in the marginal zones (Fig 2). To exclude a possibility of low-grade malignant lymphoma, a comprehensive panel of immunostainings and molecular studies were performed. No aberrant lymphoid population was present on CD3, CD5, CD10, CD20, CD23, CD43, bcl-1, bcl-2, κ, and λ immunostainings. Fluorescent in situ hybridization (FISH) analysis for the markers of mucosa-associated lymphoid tissue (MALT) lymphoma and mantle cell lymphoma was also negative: t(14;18)(q32;q21), t(11:18)(q21;q21), and 18q21 break-apart probes, all involving the MALT1 gene on chromosome 18, and t(11;14)(q13;q32) involving the CCND1 gene on chromosome 11, respectively. Gene rearrangement studies by polymerase chain reaction (PCR) method for the Ig heavy chain and T-cell receptor were also negative for any clonal population. Kaposi sarcoma-associated herpes virus immunostain for latent antigen nuclear antigen-1 staining was negative. The number of CD57-positive cells in germinal centers was markedly decreased, while the CD21-positive follicular dendritic cell network was increased in the mantle zones as well as in the germinal centers.