A pediatric-type follicular lymphoma with marginal zone and monotypic intracytoplasmic plasmacytic differentiation

Pediatric-type follicular lymphoma and pediatric nodal marginal zone lymphoma are rare indolent lymphomas that are distinctive entities with excellent prognoses. We present the histopathology and the immunophenotypic, cytogenetic, and gene rearrangement findings of a unique, heretofore, unreported case of a 15-year old boy with a right-groin mass (5.5×4.5×3.5cm) with three discrete malignant components: 1) follicular lymphoma positive for CD20, CD10, and BCL6, but negative for BCL2; by flow cytometry, 9% of the cells were kappa monotypic B-cells that expressed CD10, CD19, CD20, and CD38; 2) typical marginal zone B-cell differentiation; marginal zone B-cells were positive for CD20, CD43, BCL2, and MUM-1, but CD10 and BCL6 negative. A small subset was weakly positive for intracytoplasmic IgM and kappa consistent with early plasmacytic differentiation; 3) Plasmacytoid forms, intracytoplasmic globules and crystals strongly expressed intracytoplasmic monotypic IgM and kappa.