PMC8044963_01
Histopathological features of EBV+ EMZL. (A) Hematoxylin and eosin staining of the excisional tumor biopsy displays dense infiltrate of small to medium-sized lymphoplasmacytic cells with a vaguely nodular arrangement; (B) the higher magnification shows classic plasmacytoid cytomorphology with Dutcher bodies; (C) CD20 is positive in neoplastic cells. Note that the CD20 staining intensity is clearly lower in plasmacytoid cells than in lymphoid cells; (D, E) CD38 and MUM1 are strongly positive confirming the plasmacytic differentiation; (F) Ki-67 immunostaining demonstrates scattered positivity in the tumor cells, indicating low proliferative activity; (G) the neoplastic cells are uniformly and strongly positive for EBER. (H) Electropherograms reveal monoclonal peaks in IGH and IGK framework regions.
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Excisional biopsy revealed dense infiltrate of small to medium-sized lymphoplasmacytic cells imparting a vaguely nodular arrangement at low power ( Figure 1A ). Under high-power, 2 types of neoplastic cells were present, 1) small round to oval cells with scant pale cytoplasm and loosely clumped chromatin, 2) cells exhibited plasmacytoid appearance with Dutcher bodies ( Figure 1B ). Results showed that the neoplastic cells were diffusely immunoreactive for pan-B cell markers (CD79a, CD20, and CD19) with a lower staining intensity in the fraction of plasmacytoid cells ( Figure 1C ). As expected, the plasmacytoid cells were positive for plasma cell markers (CD38 and MUM1) ( Figures 1D, E ). Ki-67 proliferation index was estimated to be 5-10%, consistent with the indolent feature of this entity ( Figure 1F ). Figure 1G ). Further PCR-based clonal analysis disclosed clonal immunoglobulin (IG) gene rearrangement ( Figure 1H ).
A novel MAGT1 mutation identified in the current patient. (A) Family pedigree and DNA sequence chromatograms of the affected child and his parents. The proband was indicated by arrow. Confirmations of the in-frame insert mutation in MAGT1 by Sanger sequencing in the proband (top), his mother (middle), and his father (bottom). Nucleotide mutation site is marked with red circle. Reference sequence for MAGT1 gene: NM_032121.5 (B) Overview of the identified mutation. The c.828_829insAT mutant leads to a premature termination codon and generates a truncated MAGT1 protein (p.A277M.fs*11).
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Meanwhile, genetic testing of his parents indicated that the mutation was inherited from his healthy mother who was a hemizygous carrier of this variant whereas his father was wild-type ( Figure 2A ). As a result, it changes the alanine at codon 277 to methionine and introduces 10 erroneous amino acids followed by a premature stop codon TGA at codon 287 (p.A277M.fs*11) ( Figure 2B ).